Dissertations / Theses on the topic 'Precise Point Positioning'

This diploma thesis deals with the Precise Point Positioning (PPP) method in various variants. The thesis describes the theoretical foundations of the PPP method and the most important systematic errors that affect accuracy. The accuracy of the PPP method was evaluated using data from the permanent GNSS station CADM, which is part of the AdMaS research center. Data of the period 2018 – 2019 were processed. The results of combinations of different GNSS and the results of different observation periods were compared. Finally, the accuracy was verified at 299 IGS GNSS stations.

GPS processing, like every processing method for geodetic applications, relies upon least-squares estimation. Quality measures must be defined to assure that the estimates are close to reality. These quality measures are reliable provided that, first, the covariance matrix of the observations (the stochastic model) is well defined and second, the systematic effects are completely removed (i.e., the functional model is good). In the GPS precise point positioning (PPP) the stochastic and functional models are not as complicated as in the differential GPS processing. We will assess the quality of the GPS Precise Point Positioning in this thesis by trying to define more realistic standard deviations for the station position estimates. To refine the functional model from systematic errors, we have 1) used the phase observations to prevent introducing any hardware bias to the observation equations, 2) corrected observations for all systematic effects with amplitudes of more than 1cm, 3) used undifferenced observations to prevent having complications (e.g. linearly related parameters) in the system of observation equations. To have a realistic covariance matrix for the observations we have incorporated the ephemeris uncertainties into the system of observation equations. Based on the above-mentioned issues a PPP processing method is designed and numerically tested on the real data of some of the International GNSS Service stations. The results confirm that undifferenced stochastic-related properties (e.g. degrees of freedom) can be reliable means to recognize the parameterization problem in differenced observation equations. These results also imply that incorporation of the satellite ephemeris uncertainties might improve the estimates of the station positions. The effect of troposphere on the GPS data is also focused in this thesis. Of particular importance is the parameterization problem of the wet troposphere in the observation equations.

QC 20130218

Utvecklingen av satellitbaserad positionsbestämning gör det idag befogat att begära låga osäkerheter med GNSS. Det är idag möjligt att uppnå osäkerheter kring centimetern. Bäst mätosäkerhet ger relativ mätning som sker med stöd av antingen enkelstations- eller nätverks-RTK. I Sverige erbjuder Lantmäteriet med sitt SWEPOS ett tätt referensnätverk som förser användaren med korrektionsdata oavsett position inom Sveriges gränser. Dock är det inte alla länder som kan erbjuda denna positionstjänst. Geografiskt stora länder har mycket svårt att skapa ett referensnät, det skulle betyda flera tusen stationer och gör det till en ekonomisk fråga. Det är bl.a. ur den synpunkten andra metoder har växt fram. En av dessa är Precise Point Positioning (PPP). Enligt G. Hedling (personlig kommunikation, 18 mars 2015) har PPP fått en väl etablering inom jordbruket samt på maritima gruv- och oljeplattformar. Metoden är lämplig vid stora öppna ytor och när avståndet till närmsta referensstation är stor. PPP använder sig av absolut positionering och kan mäta både statiskt och kinematiskt och resultat kan fås i realtid och genom efterberäkning. Det ligger i Lantmäteriets intresse att testa kinematisk PPP i Sverige och den här studien testar kinematisk PPP i realtid med programvaran BNC 2.11 och med korrektioner från International GPS Service (IGS). Enligt Bisnath & Gao (2009) erhålls decimeterosäkerhet med kinematisk PPP och för att bestämma dess tillförlitlighet har i den här studien koordinatavvikelse beräknats mellan BNC och enkelstations-RTK med stöd från SWEPOS. Koordinaterna från enkelstations-RTK har vid testerna angivits som de sanna koordinaterna, genom ett statiskt test har det undersökts om det är motiverat. Utifrån den statiska mätningen har även intialiseringstiden kunnat utredas, alltså den tid det tar för PPP att konvergera. Efterberäkningstjänsten CSRS-PPP har också testats och jämförts mot kända koordinater vid den statiska mätningen.Studien visar att efter närmare en timmes observation avviker PPP under 2 dm i plan mot enkelstations-RTK. Den visar också att 15-30 minuters konvergeringstid är nödvändig för att erhålla osäkerheter på några decimeter. Några av de faktorer som påverkar resultatet är bl.a. jonosfärstörning. högt PDOP-värde och antal processerade satelliter i mjukvarorna, hur mycket är svårt att säga. Vid en tappad signal krävs en ny omintialisering på flera tiotals minuter. Studien visar också att det är lämpligt att använda enkelstations-RTK som sanning. Vid den statiska mätningen avviker enkelstations-RTK kring centimetern mot den kända punktens koordinater, vilket anses godtagbart. CSRS-PPP uppvisar bra resultat och är inte mycket sämre än det resultat enkelstations-RTK redovisar.
Today it´s possible to achieve low uncertainties when surveying with GNSS. You can expect uncertainties around centimeter-level. The best results are achieved when using relative-surveying with corrections from single-station- or network-RTK. The Swedish mapping, cadastral and land registration authority (Lantmäteriet) is providing a well-developed network of reference stations. The network, called SWEPOS, offers corrections for its users independent of position within the Swedish borders. Far from all nations has the ability or the financial resources to create such an expanded network. Instead, other methods for satellite surveying have been developed, including Precise Point Positioning (PPP). According to G. Hedling (personal communication, 18 march 2015) PPP is well-established in the agriculture and in the maritime mining- and oil-industry. The method is suitable in open areas and it is independently of nearby reference stations. PPP is using what’s called absolute-surveying. The surveying is performed either kinematic or static and the results can be obtained thru post-processing or in real-time. “Lantmäteriet” has interest in testing kinematic PPP in Sweden and for this thesis kinematic PPP in real-time is tested with BNC 2.11 software and corrections is given from the International GPS Service (IGS). According to Bisnath & Gao (2009) it is possible to achieve uncertainties in decimeter-level with kinematic PPP. To determine the reliability of PPP the deviation has been calculated against single-station-RTK. The single-station-RTK coordinates have in this study been used as the “truth” and in an additional test using static measurements it has been investigated if that’s correct. From the static test the initialization time for PPP as well as the quality of the post-processing service CSRS-PPP has been studied.The results show that after nearly an hour of observation the deviation between PPP and single-station-RTK are below 2 dm for the level-coordinates. The initialization time of 15-30 minutes is necessary to achieve uncertainties of a few decimeters. Elements that are affecting the results are disturbance in the ionosphere, high PDOP and number of processed satellites in the software. In which extent it’s not possible to determine. When the signal is lost between rover and satellites a re-initialization of 15-30 minutes is needed. It also shows that it is reasonable to use single-station-RTK as the “truth”. Single-station-RTK deviates a proximately one centimeter in relation to known coordinates. The post-processing service CSRS-PPP gives remarkably good results not far from what single-station-RTK offers.

Vid GNSS-positionering i samband med fastighetsbildningsåtgärder används vanligtvis den traditionella RTK-mätningen (Real-Time Kinematic) via SWEPOS nätverks-RTK-tjänst. Denna tjänst kräver mobiltelefontäckning eller motsvarande tvåvägskommunikation, vilket kan vara problematiskt inom områden med bristfällig mobiltelefontäckning. Under dessa förhållanden kan istället PPP-mätning (Precise Point Positioning) vara användbart vid fastighetsbildningsåtgärder då dessa tjänster tar emot korrektionsdata i realtid från satelliter. PPP kräver inte någon mobiltelefontäckning, däremot krävs en kommunikationslänk, en RTX-tjänst för att erhålla korrektioner externt från en RTX-satellit. Syftet med studien är att undersöka möjligheten till att nyttja PPP i realtid vid fastighetsbildningsåtgärder som ett alternativ till traditionell GNSS-mätning med nätverks-RTK. För att PPP ska vara ett alternativ till traditionell GNSS-mätning i realtid krävs det att mätosäkerhetskraven inom fastighetsbildning uppfylls. Mätosäkerheten undersöktes genom att utgå ifrån redan kända koordinater (RIX 95-punkter). Mätningarna har genomförts på fem olika platser i Sverige, Göteborg, Vänersborg, Karlstad, Torsby och Malung-Sälen. Mätdata som erhölls från undersökningsplatserna har analyserats samt jämförts med fastighetsbildningskraven. Resultatet av studien erhölls i form av analyserad mätdata med jämförelser mot redan kända (RIX 95) punkter. Avikelsen från känd RIX 95-punkt redovisas i resultatet utifrån tidsaspekten, den systematiska avvikelsen av translativ art, förändringar i avvikelsen från söder till norr samt utifrån två beräkningsmodeller, varav en translation och en transformation. För att få den erhållna mätdatan från RTX-tjänsten att överensstämma bättre med referenspunkten (RIX 95-punkten) togs beräkningsmodellerna fram för att möjliggöra modellering av systematiska avvikelser som uppkommit och därmed uppfylla kraven inom fasighetsbildningsåtgärder. Genom att ha analyserat och granskat olika samband har det framkommit att efter ca 20 minuters mätning, börjar precisionen för mätningarna att bli stabila. Utifrån resultatet är slutsatsen att PPP inte fungerar vid fastighetsbildningsåtgärder för områden inom stomnät, däremot fungerar metoden för skogs- och jordbruksfastigheter utanför stomnät. Förutsatt att en modellering genom translation alternativt transformation som är framtagen i denna studie används för att justera koordinaterna så fungerar PPP-mätning inom samtliga fastighetsbildningsåtgärder. Detta kräver då att mätdata erhålls efter 20 minuters mätning eller mer.
GNSS positioning in conjunction with the real property is usually used the traditional RTK measuring (Real-Time Kinematic) by SWEPOS network RTK service. This service requires mobile phone coverage or equivalent two-way communication, which can be problematic in areas with poor mobile phone coverage. Under these circumstances, PPP (Point Positioning Precise) could be more useful in real property measures when such services receives the correction data in real time from the satellites. PPP does not require any cell phone coverage, however it requires a communication link, a RTX service to obtain corrections externally from a RTX satellite. The purpose of the study is to examine the possibility of using PPP in real time at the real property as an alternative to traditional GNSS measurements with network RTK. The measurement uncertainty was investigated by starting out from already known coordinates (RIX 95 points). The measurements were performed out at five different locations in Sweden, Gothenburg, Vanersborg, Karlstad, Torsby and Malung-Salen. Measurement data obtained from the observations have been analyzed and compared with real property requirements. The results of the study were obtained in the form of data analyzed by comparison of the known (RIX 95) points. The deviation is known from RIX 95 point recognized in income based on the time factor, the bias of the translative case species, changes in deviation from south to north and from two calculation models, a translation and a transformation. To correct the measured values from the RTX service for a better match to the RIX 95 points calculation models were developed to facilitate the modeling of systematic deviations incurred and meet the demands of real property. Analyzing and examining various relationships have shown that after about 20 minutes of measuring, the precision of the measurements starts to become more stable. Based on the results, the conclusion is that the PPP does not work in real property areas within the core network, however, the method works for forestry and agricultural properties outside the core network. Assuming a modelling through translational alternative transformation, developed in this study is used to adjust the coordinates, the PPP measurement is working in all real property registration measures. This requires that the measurement data is obtained after 20 minutes of measurement or more.

Precise Point Positioning (PPP) provides GNSS navigation using a stand-alone receiver with no base station. As a technique PPP suffers from long convergence times and quality degradation during periods of poor satellite visibility or geometry. Many applications require reliable realtime centimetre level positioning with worldwide coverage, and a short initialisation time. To achieve these goals, this thesis considers the use of GLONASS in conjunction with GPS in kinematic PPP. This increases the number of satellites visible to the receiver, improving the geometry of the visible satellite constellation. To assess the impact of using GLONASS with PPP, it was necessary to build a real time mode PPP program. pppncl was constructed using a combination of Fortran and Python to be capable of processing GNSS observations with precise satellite ephemeris data in the standardised RINEX and SP3 formats respectively. pppncl was validated in GPS mode using both static sites and kinematic datasets. In GPS only mode, one sigma accuracy of 6.4mm and 13mm in the horizontal and vertical respectively for 24h static positioning was seen. Kinematic horizontal and vertical accuracies of 21mm and 33mm were demonstrated. pppncl was extended to assess the impact of using GLONASS observations in addition to GPS in static and kinematic PPP. Using ESA and Veripos Apex G2 satellite orbit and clock products, the average time until 10cm 1D static accuracy was achieved, over a range of globally distributed sites, was seen to reduce by up to 47%. Kinematic positioning was tested for different modes of transport using real world datasets. GPS/GLONAS SPPP reduced the convergence time to decimetre accuracy by up to a factor of three. Positioning was seen to be more robust in comparison to GPS only PPP, primarily due to cycle slips not being present on both satellite systems on the occasions when they occurred, and the reduced impact of undetected outliers.

Precise Point Positioning (PPP) ermöglicht eine präzise Positionsbestimmung mittels globaler Satellitennavigationssysteme (Global Navigation Satellite System, GNSS) ohne die direkte Verwendung der Beobachtungsdaten von regionalen Referenzstationen. Die wesentlichste Einschränkung von PPP im Vergleich zu differenziellen Auswertetechniken (Real-Time Kinematic, RTK) ist die deutlich längere Konvergenzzeit. Voraussetzung für die Verkürzung der Konvergenzzeit ist die Festsetzung der geschätzten Mehrdeutigkeiten auf ganzzahlige Werte. Die Mehrdeutigkeitslösung verlangt ein robustes funktionales Modell und beruht auf einem zweistufigen Mehrdeutigkeitsfestsetzungsverfahren, welches frei von ionosphärischen Einflüssen 1. Ordnung ist. Die sowohl auf Code- als auch auf Phasenbeobachtungen basierende Melbourne-Wübbena-Linearkombination erlaubt hierbei eine einfache Festsetzung der Widelane-Mehrdeutigkeiten. Infolgedessen kann zur Berechnung der ionosphären-freien Linearkombination die im Vergleich zur Wellenlänge der ionosphären-freien Linearkombination deutlich größere Narrowlane-Wellenlänge verwendet werden. Zur Stabilisierung des im Normalfall lediglich auf den Beobachtungsdaten des amerikanischen Global Positioning System (GPS) beruhenden funktionalen Modells können die Beobachtungsdaten des russischen GLObal’naya NAvigatsioannaya Sputnikovaya Sistema (GLONASS) beitragen. Aufgrund der Technik, die GLONASS zur Identifizierung der einzelnen Satelliten einsetzt (Frequency Division Multiple Access, FDMA), unterscheiden sich die Frequenzen der einzelnen Satelliten. Die leicht unterschiedlichen Frequenzen erschweren die Modellierung und Korrektion der instrumentell bedingten Signalverzögerungen (z. B. Fractional-Cycle Biases (FCB)). Vor diesem Hintergrund kann das konventionelle Mehrdeutigkeitsfestsetzungsverfahren nur bedingt für GLONASS verwendet werden. Die Untersuchung der instrumentell bedingten GLONASS-Signalverzögerungen sowie die Entwicklung einer alternativen Methode zur Festsetzung der GLONASS-Mehrdeutigkeiten mit dem Ziel einer kombinierten GPS/GLONASS-Mehrdeutigkeitslösung sind die Schwerpunkte der vorliegenden Arbeit. Die entwickelte alternative Mehrdeutigkeitsfestsetzungsstrategie baut auf der puren Widelane-Linearkombination auf, weshalb globale Ionosphärenmodelle unabdingbar sind. Sie eignet sich sowohl für GLONASS als auch für GPS und zeigt gleichwertige Ergebnisse für beide GNSS, wenngleich im Vergleich zur konventionellen Methode mit geringeren Mehrdeutigkeitsfestsetzungsquoten zu rechnen ist
Precise Point Positioning (PPP) allows for accurate Global Navigation Satellite System (GNSS) based positioning without the immediate need for observations collected by regional station networks. The fundamental drawback of PPP in comparison to differential techniques such as Real-Time Kinematic (RTK) is a significant increase in convergence time. Among a plurality of different measures aiming for a reduction of convergence time, fixing the estimated carrier phase ambiguities to integer values is the key technique for success. The ambiguity resolution asks for a robust functional model and rests upon a two-stage method ruling out first-order ionospheric effects. In this context the Melbourne-Wübbena linear combination of dual-frequency carrier phase and code measurements leverages a simple resolution of widelane ambiguities. As a consequence the in comparison to the wavelength of the ionosphere-free linear combination significantly longer narrowlane wavelength can be used to form the ionosphere-free linear combination. By default the applied functional model is solely based on observations of the Global Positioning System (GPS). However measurements from the GLObal’naya NAvigatsioannaya Sputnikovaya Sistema (GLONASS) can contribute to improve the model’s stability significantly. Due to the technique used by GLONASS to distinguish individual satellites (Frequency Division Multiple Access, FDMA), the signals broadcast by those satellites differ in their frequencies. The resulting slightly different frequencies constitute a barricade for both modelling and correcting any device-dependent signal delays, e.g. fractional-cycle biases (FCB). These facts limit the applicability of the conventional ambiguity-fixing approach when it comes to GLONASS signals. The present work puts a focus both on investigating the device-dependent GLONASS signal delays and on developing an alternative method for fixing GLONASS ambiguities with the ultimate objective of a combined GPS/GLONASS ambiguity resolution. The alternative ambiguity resolution strategy is based on the pure widelane linear combination, for which reason ionospheric corrections are indispensable. The procedure is applicable for GLONASS in the first instance but reveals equivalent results for both GPS and GLONASS. The disadvantage relative to the conventional approach is the reduced ambiguity fixing success rate

GPS precise point positioning (PPP) has been used in many scientific and commercial applications due to its high computational efficiency, no need for any synchronous measurements from a nearby reference receiver and homogeneous positioning quality on a global scale. However, these merits are devalued significantly by unresolved ambiguities and slow convergences of PPP. Therefore, this thesis aims at improving PPP’s performance by resolving ambiguities for a single receiver and accelerating the convergences to ambiguity-fixed solutions in order to achieve a centimeter-level positioning accuracy with only a few seconds of measurements. In recent years, ambiguity resolution for PPP has been developed by separating fractional cycle biases (FCBs) from single-receiver ambiguity estimates. One method is to estimate FCBs by averaging the fractional parts of single-difference ambiguity estimates between satellites, and the other is to assimilate FCBs into clocks by fixing undifferenced ambiguities to integers in advance. The first method suffers from a large number of redundant satellite-pair FCBs and unnecessary 15-minute narrow-lane FCBs. Therefore, this thesis suggests undifferenced FCBs and one narrow-lane FCB per satellite-pair pass over a regional area in order to reduce the size of FCB products and achieve comparable positioning quality with that of the original method. Typical tests show that ambiguity resolution dramatically reduces the RMS of differences between hourly and daily position estimates from 3.8, 1.5 and 2.8 cm in ambiguity-float solutions to 0.5, 0.5 and 1.4 cm in ambiguity-fixed solutions for the East, North and Up components, respectively. Likewise, the RMS for real-time position estimates are reduced drastically from 13.7, 7.1 and 11.4 cm to 0.8, 0.9 and 2.5 cm. Of particular note, this improvement can be achieved even at remote receivers which are over a few thousand kilometers from the reference receivers that are used to estimate FCBs. Furthermore, this thesis improves the accuracy of narrow-lane FCB estimates with integer constraints from double-difference ambiguities. In a one-year global network analysis, the RMS of differences for the East component between the daily and IGS weekly estimates is reduced from 2.6 mm in the solutions based on original FCBs to 2.2 mm in the solutions based on improved FCBs. Although small, this improvement is significant and critical to some geophysical studies, such as tectonic motions, sea level rise, and post-glacial rebound. More importantly, for the first time, this thesis provides a theoretical proof for the equivalence between the ambiguity-fixed position estimates derived from the aforementioned two methods. This equivalence is then empirically verified by the overall minimal discrepancies of the positioning qualities between the two methods. However, these discrepancies manifest a distribution of geographical pattern, i.e. the largest discrepancies correspond to sparse networks of reference receivers. This comparison can provide valuable reference for the GPS community to choose an appropriate method for their PPP ambiguity resolution. As the foremost contribution, an innovative method is originally developed in this thesis in order to effectively re-converge to ambiguity-fixed solutions with only a few seconds of measurements. Specifically, ionospheric delays at all ambiguity-fixed epochs are estimated and then predicted precisely to succeeding epochs in the case of re-convergences. The predicted ionospheric delays are first used to correct wide-lane measurements in order to rapidly resolve wide-lane ambiguities. The resulting ionosphere-corrected and ambiguity-fixed wide-lane measurements are then used to tightly constrain narrow-lane measurements and thus speed up narrow-lane ambiguity resolution significantly. As a result, the practicability of real-time PPP is greatly improved by eliminating the unrealistic requirement of a continuous open sky view in most PPP applications. Typical tests illustrate that over 90% of re-convergences can be achieved within five epochs of 1-Hz measurements, rather than the conventional 20 minutes, even if the latency for the predicted ionospheric delays is up to 180 s. Moreover, for a van-borne receiver moving in a GPS-adverse environment where satellite number decreases significantly and cycle slips occur frequently, only when the above rapid re-convergence technique is applied can the rate of ambiguity-fixed epochs dramatically rise from 7.7% to 93.6% of all epochs. Finally, a precise positioning service for the next-generation global RTK, characterized by both global coverage and regional augmentation, is originally proposed in this thesis based on real-time PPP enhanced by rapid (re-)convergences to ambiguity-fixed solutions. It is illustrated that a globally distributed network of 38 stations can ensure that the ambiguity-fixed epochs account for over 95% of all epochs.

In this thesis we study the principles and intricacies of the new state-of-the-art precise positioning technique, the PPP-RTK. Both its network- and user-components are discussed. The concept of array-based PPP-RTK is introduced, where its efficiency is demonstrated by multi-Global Navigation Satellite Systems (GNSS) results. Finally an optimal recursive filter is developed to process observation equations of the network- and user-components.

Centimetre-level Global Navigation Satellite System (GNSS) based positioning is increasingly relevant for a large number of applications. Currently, this level of GNSS positioning accuracy is most commonly achieved using the conventional Real Time Kinematic (cRTK) method. In order to achieve such high-accuracies with cRTK, the distance (baseline) between the user and reference station must typically be shorter than 50 km for dual-frequency GNSS receivers. To address the limitations of cRTK, the Precise Point Positioning (PPP) method, which does not require local reference networks, was developed. The principle of PPP is to model and correct error sources such as satellite orbit and clock errors using correction products and error modelling. PPP is not currently suitable for many applications, because of the long solution convergence time (from 20 to 60 min to achieve 10 cm accuracy), insufficient positioning accuracies and a lack of integrity monitoring. Current fixed ambiguity PPP methods are analysed and tested using the National Oceanic and Atmospheric Administration (NOAA) dataset in this thesis. Based on the analysis, the most reliable existing validation method has unacceptably large rate (12.7%) of incorrect ambiguity resolution. Therefore, this thesis develops an enhanced PPP method. The enhanced PPP method is based on using the enhanced ambiguity validation method (e.g. time-window based validation) and employing both GLONASS and GPS measurements to calculate a float position solution. In addition, integrity monitoring is improved in terms of failure exclusion and protection level calculation. When employing the enhanced PPP method, the rate of incorrect ambiguity resolution decreases to 5.3% and of correct ambiguity resolution increases to 82.2% when using the (NOAA) dataset. The average horizontal, vertical and 3D position errors at the initial ambiguity resolution epoch are reduced by 40.0%, 23.8% and 31.8%, respectively, compared to the most reliable existing PPP method.

For earthquake and tsunami early-warning, it is crucial that displacements resulting from earthquakes are recorded with speed and accuracy. Traditional methods based on seismometer data often suffer from errors during integration which results in the maximum displacement not being accurately recorded. In contrast, Global Navigation Satellite Systems (GNSS) can measure permanent static displacement directly; however it too is subject to errors, the main error of which is multipath. Multipath can lead to errors in the measurement of small displacements or mask the displacement completely. Multipath is dependent on the geometry of the GNSS constellation orbits and the antenna’s surrounds. GPS satellites have an orbital period of half a sidereal day with a near-sidereal repeating ground track. Similarly, the GLONASS constellation geometry repeats about once every eight sidereal days thus the satellite-reflector geometry will repeat with these same periods. By accurately determining the repeat periods it is possible to remove the multipath error by analysing data from the previous repeat periods. This method is known as sidereal filtering and can be used to improve the precision of GNSS coordinate time series and hence improve displacement measurements. This thesis looks to find the optimum geometry repeat period for the GLONASS constellation, which was found to be 689248 s and combine GPS and GLONASS for observation domain near-sidereal filtering. GLONASS-only filtering improves GLONASS coordinate solution standard deviations, on average, by 22.3%, 18.1% and 17.6% in the East, North and Up, whereas GPS and GLONASS combined filtering improves GPS and GLONASS standard deviations by 21.2%, 23.4% and 25.1%. The average maximum stability improvement, in terms of Allan deviation for all components is approximately 21.0% for GLONASS-only and 29.0% for combined filtering. Combined filtering produces more stable coordinate time series for averaging intervals over a few hundred seconds. It also reduces coordinate time series standard deviations and thus aids the measurement of small coordinate displacements and reduces the number of false alarms by half during displacement detection. Filtering improves the accuracy and precision of displacement estimates on average by about 2 mm, in terms of the difference between filtered and unfiltered RMSD and mean displacement values.

The main drawback of Precise Point Positioning (PPP) is a long convergence time. This thesis integrates Multi-Frequency Multi-Constellation (MFMC) GNSS data to improve PPP convergence. The biases that occur during data integration were identified and modelled. Triple-frequency data was used to improve both float ambiguity and integer ambiguity resolution PPP models. Precise atmospheric products were investigated for constraining the ionosphere and troposphere errors. A method was proposed for maintaining decimetre accuracy during communication outages.

GPS processing, like every processing method for geodetic applications, relies upon least-squares estimation. Quality measures must be defined to assure that the estimates are close to reality. These quality measures are reliable provided that, first, the covariance matrix of the observations (the stochastic model) is well defined and second, the systematic effects are completely removed (i.e., the functional model is good). In the GPS precise point positioning (PPP) the stochastic and functional models are not as complicated as in the differential GPS processing. We will assess the quality of the GPS Precise Point Positioning in this thesis. To refine the functional model from systematic errors, we have 1) used the phase observations to prevent introducing any hardware bias to the observation equations, 2) corrected observations for all systematic effects with amplitudes of more than 1cm, 3) used undifferenced observations to prevent having complications (e.g. linearly related parameters) in the system of observation equations. To have a realistic covariance matrix for the observations we have incorporated the ephemeris’ uncertainties into the system of observation equations. The above-mentioned technique is numerically tested on the real data of some of the International GNSS Service stations. The results confirm that undifferenced stochastic-related properties (e.g. degrees of freedom) can be reliable means to recognize the parameterization problem in differenced observation equations. These results also imply that incorporation of the satellite ephemeris uncertainties might improve the estimates of the station positions.
QC 20120503

This thesis investigates the major errors and processes affecting the performance of a viable, standalone point positioning technique known as single frequency Precise Point Positioning (PPP). The PPP processing utilises both single frequency code and carrier phase GPS observables. The mathematical model implemented is known as the code and quasi-phase combination. Effective measures to improve the quality of the positioning solutions are assessed and proposed. The a priori observations sigma (or standard deviation) ratio in the sequential least squares adjustment model plays a significant role in determining the accuracy and precision of the estimated solutions, as well as the solutions convergence time. An

ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NV
The use of differential GPS post-procesing for precise trajectography computation has been widely used since early 90s. Up to recent dates, installation of a GPS receiver in a well known position (base station) has been mandatory. Operating range from this base station varies from 50 km up to 100 km, depending on the accuracy required, which impose single or dual frequency GPS technique. Nowadays, the huge amount of GPS base stations continuous logging data worldwide have allowed to improve the error models a lot. Using these precise models, it is possible to achieve centimeter accuracy in GPS trajectography by using only one GPS receiver without range to a base station restrictions. This technique is called Precise Point Positioning (PPP). The performance results for PPP obtained after a real 10 flights campaign will be presented.

Esta tesis doctoral llevó a cabo el estudio, desarrollo e implementación de algoritmos para la navegación con sistemas globales de navegación por satélite (GNSS), enfocándose en la determinación precisa de la posición, velocidad y aceleración usando GPS, en modo post-procesado y lejos de estaciones de referencia. Uno de los objetivos era desarrollar herramientas en esta área y hacerlas disponibles a la comunidad GNSS. Por ello el desarrollo se hizo dentro del marco del proyecto preexistente de software libre llamado GPS Toolkit (GPSTk). Una de las primeras tareas realizadas fue la validación de las capacidades de la GPSTk para el procesado del pseudorango, realizando comparaciones con una herramienta de procesamiento de datos probada (BRUS). La gestión de datos GNSS demostró ser un asunto importante cuando se intentó extender las capacidades de la GPSTk al procesamiento de datos obtenidos de las fases de la señal GPS. Por ello se desarrollaron las Estructuras de Datos GNSS (GDS), que combinadas con su paradigma de procesamiento aceleran el proceso de desarrollo de software y reducen errores. La extensión de la GPSTk a los algoritmos de procesado en fase se hizo mediante la ayuda de las GDS, proporcionándose importantes clases accesorias que facilitan el trabajo. Se implementó el procesado de datos Precise Point Positioning (PPP) con ejemplos relativamente simples basados en las GDS, y al comparar sus resultados con otras aplicaciones de reputación ya establecida, se encontró que destacan entre los mejores. También se estudió cómo obtener la posición precisa, en post-proceso, de un receptor GPS a cientos de kilómetros de la estación de referencia más cercana y usando tasas de datos arbitrarias (una limitación del método PPP). Las ventajas aportadas por las GDS permitieron la implementación de un procesado semejante a un PPP cinemático basado en una red de estaciones de referencia, estrategia bautizada como Precise Orbits Positioning (POP) porque sólo necesita órbitas precisas para trabajar y es independiente de la información de los relojes de los satélites GPS. Los resultados de este enfoque fueron muy similares a los del método PPP cinemático estándar, pero proporcionando soluciones de posición con una tasa mayor y de manera más robusta. La última parte se enfocó en la implementación y mejora de algoritmos para determinar con precisión la velocidad y aceleración de un receptor GPS. Se hizo énfasis en el método de las fases de Kennedy debido a su buen rendimiento, desarrollando una implementación de referencia y demostrando la existencia de una falla en el procedimiento propuesto originalmente para el cálculo de las velocidades de los satélites. Se propuso entonces una modificación relativamente sencilla que redujo en un factor mayor que 35 el RMS de los errores 3D en velocidad. Tomando ideas de los métodos Kennedy y POP se desarrolló e implementó un nuevo procedimiento de determinación de velocidad y aceleración que extiende el alcance. Este método fue llamado Extended Velocity and Acceleration determination (EVA). Un experimento usando una aeronave ligera volando sobre los Pirineos mostró que tanto el método de Kennedy (modificado) como el método EVA son capaces de responder ante la dinámica de este tipo de vuelos. Finalmente, tanto el método de Kennedy modificado como el método EVA fueron aplicados a una red en la zona ecuatorial de Sur América con líneas de base mayores a 1770 km. En este escenario el método EVA mostró una clara ventaja tanto en los promedios como en las desviaciones estándar para todas las componentes de la velocidad y la aceleración.
This Ph.D. Thesis focuses on the development of algorithms and tools for precise GPS-based position, velocity and acceleration determination very far from reference stations in post-process mode. One of the goals of this thesis was to develop a set of state-of-the-art GNSS data processing tools, and make them available for the research community. Therefore, the software development effort was done within the frame of a preexistent open source project called the GPSTk. Therefore, validation of the GPSTk pseudorange-based processing capabilities with a trusted GPS data processing tool was one of the initial task carried out in this work. GNSS data management proved to be an important issue when trying to extend GPSTk capabilities to carrier phasebased data processing algorithms. In order to tackle this problem the GNSS Data Structures (GDS) and their associated processing paradigm were developed. With this approach the GNSS data processing becomes like an assembly line, providing an easy and straightforward way to write clean, simple to read and use software that speeds up development and reduces errors. The extension of GPSTk capabilities to carrier phase-based data processing algorithms was carried out with the help of the GDS, adding important accessory classes necessary for this kind of data processing and providing reference implementations. The performance comparison of these relatively simple GDS-based source code examples with other state-of-the art Precise Point Positioning (PPP) suites demonstrated that their results are among the best. Furthermore, given that the GDS design is based on data abstraction, it allows a very flexible handling of concepts beyond mere data encapsulation, including programmable general solvers, among others. The problem of post-process precise positioning of GPS receivers hundreds of kilometers away from nearest reference station at arbitrary data rates was dealt with, overcoming an important limitation of classical post-processing strategies like PPP. The advantages of GDS data abstraction regarding solvers were used to implement a kinematic PPP-like processing based on a network of stations. This procedure was named Precise Orbits Positioning (POP) because it is independent of precise clock information and it only needs precise orbits to work. The results from this approach were very similar (as expected) to the standard kinematic PPP processing strategy, but yielding a higher positioning rate. Also, the network-based processing of POP seems to provide additional robustness to the results, even for receivers outside the network area. The last part of this thesis focused on implementing, improving and testing algorithms for the precise determination of velocity and acceleration hundreds of kilometers away from nearest reference station. Special emphasis was done on the Kennedy method because of its good performance. A reference implementation of Kennedy method was developed, and several experiments were carried out. Experiments done with very short baselines showed a flaw in the way satellite velocities were computed, introducing biases in the velocity solution. A relatively simple modification was proposed, and it reduced the RMS of 5-min average velocity 3D errors by a factor of over 35. Then, borrowing ideas from Kennedy method and the POP method, a new velocity and acceleration determination procedure named EVA was developed and implemented that greatly extends the effective range. An experiment using a light aircraft flying over the Pyrenees showed that both the modified-Kennedy and EVA methods were able to cope with the dynamics of this type of flight. Finally, both modified-Kennedy and EVA method were applied to a challenging scenario in equatorial South America, with baselines over 1770 km, where EVA method showed a clear advantage in both averages and standard deviations for all components of velocity and acceleration. Lloc i

The research of this paper-based dissertation is focused on the Fast Precise Point Positioning (Fast-PPP) technique. The novelty relies on using an accurate ionosphere model, in combination with the standard precise satellite clock and orbit products, to reduce the convergence time of state-of-the-art high-accuracy navigation techniques from approximately one hour to few minutes. My first contribution to the Fast-PPP technique as a Ph.D. student has been the design and implementation of a novel user navigation filter, based on the raw treatment of undifferenced multi-frequency code and carrier-phase Global Navigation Satellite System (GNSS) measurements. The innovative strategy of the filter avoids applying the usual ionospheric-free combination to the GNSS observables, exploiting the full capacity of new multi-frequency signals and increasing the robustness of Fast-PPP in challenging environments where the sky visibility is reduced. It has been optimised to take advantage of the corrections required to compensate the delays (i.e., errors) affecting the GNSS signals. The Fast-PPP corrections, and most important, their corrections uncertainties (i.e., the confidence bounds) are added as additional equations in the navigation filter to obtain Precise Point Positioning (PPP) in few minutes. A second contribution performed with the new user filter, has been the consolidation of the precise ionospheric modelling of Fast-PPP and its extension from a regional to a global scale. The correct use of the confidence bounds has been found of great importance when navigating in the low-latitude areas of the equator, where the ionosphere is difficult to be accurately modelled. Even in such scenario, a great consistency has been achieved between the actual positioning errors with respect to the formal errors, as demonstrated using similar figures of merit used in civil aviation, as the Stanford plot. A third contribution within this dissertation has been the characterisation of the accuracy of different ionospheric models currently used in GNSS. The assessment uses actual, unambiguous and undifferenced carrier-phase measurements, thanks to the centimetre-level modelling capability within the Fast-PPP technique. Not only the errors of the ionosphere models have been quantified in absolute and relative terms, but also, their effect on navigation.
La investigació d'aquesta Tesi Doctoral per compendi d'articles es centra en la tècnica de ràpid Posicionament de Punt Precís (Fast-PPP). La novetat radica en l'ús d'un model ionosfèric precís que, combinat amb productes estàndard de rellotge i de l'òrbita de satèl·lit, redueix el temps de convergència de les actuals tècniques de navegació precisa d'aproximadament una hora a pocs minuts. La meva primera contribució a la tècnica Fast-PPP com a estudiant de Doctorat ha estat el disseny i la implementació d'un filtre de navegació d'usuari innovador, basat en el tractament de múltiples freqüències de mesures de codi i fase sense diferenciar (absolutes). La estratègia del filltre de navegació evita l'aplicació de l'habitual combinació lineal lliure de ionosfera per a aquests observables. Així, s'explota la capacitat completa dels senyals multi-freqüència en el nous Sistemes Globals de Navegació per Satèl·lit (GNSS) i s'augmenta la robustesa del Fast-PPP en entorns difícils, on es redueix la visibilitat del cel. S'ha optimitzat per tal de prendre avantatge de les correccions necessàries per a compensar els retards (és a dir, els errors) que afecten els senyals GNSS. Les correccions de Fast-PPP i més important, les seves incerteses (és a dir, els intervals de confiança) s'afegeixen com a equacions addicionals al filltre per aconseguir Posicionat de Punt Precís (PPP) en pocs minuts. La segona contribució ha estat la consolidació del modelat ionosfèric precís de Fast-PPP i la seva extensió d'un abast regional a una escala global. La correcta determinació i ús dels intervals de confiança de les correccions Fast-PPP ha esdevingut de gran importància a l'hora de navegar en zones de baixa latitud a l'equador, on la ionosfera és més difícil de modelar amb precisió. Fins i tot en aquest escenari, s'ha aconseguit una gran consistència entre els errors de posicionament reals i els nivells de protecció dels usuaris de Fast-PPP, tal com s'ha demostrat amb figures de mèrit similars a les utilitzades en l'aviació civil (els diagrames de Stanford). La tercera contribució d'aquesta Tesi Doctoral ha estat la caracterització de l'exactitud dels models ionosfèrics utilitzats actualment en GNSS. L'avaluació utilitza mesures de fase, sense ambigüitats i sense diferenciar, gràcies a la capacitat de modelatge centimètric emprat a la tècnica de Fast-PPP. No només els errors dels models de la ionosfera han estat quantificats en termes absoluts i relatius, sinó també, el seu efecte sobre la navegació
La investigación de esta Tesis Doctoral, por compendio de artículos, se centra en la técnica de rápido Posicionamiento de Punto Preciso (Fast-PPP). La novedad, radica en el uso de un modelo ionosférico preciso que, combinado con productos estándard de reloj y órbita de satélite, reduce el tiempo de convergencia de las actuales técnicas de navegación precisa de una hora a pocos minutos.Mi primera contribución a la técnica Fast-PPP como estudiante de Doctorado ha sido el diseño y la implementación de un filtro de navegación de usuario innovador, basado en el tratamiento de múltiples frecuencias de medidas de código y fase sin diferenciar (absolutas). La estrategia del filtro de navegación evita la aplicación de la habitual combinación lineal libre de ionosfera para dichos observables. Así, se explota la capacidad de la señal multi-frecuencia en los nuevos Sistemas Globales de Navegación por Satélite (GNSS) y se aumenta la robustez del Fast-PPP en entornos difíciles, donde se reduce la visibilidad del cielo. Se ha optimizado para tomar ventaja de las correcciones necesarias para compensar los retardos (es decir, los errores) que afectan las señales GNSS. Las correcciones de Fast-PPP y más importante, sus incertidumbres (es decir, los intervalos de confianza) se añaden como ecuaciones adicionales al filtro para conseguir Posicionamiento de Punto Preciso (PPP) en pocos minutos. La segunda contribución ha estado la consolidación del modelado ionosférico preciso de Fast-PPP y la extensión de su cobertura regional a una escala global. La correcta determinación y uso de los intervalos de confianza de las correcciones Fast-PPP ha sido de gran importancia a la hora de navegar en zonas de latitudes ecuatoriales, donde la ionosfera es más difícil de modelar con precisión. Incluso en dicho escenario, se ha conseguido una gran consistencia entre los errores de posicionamiento reales y los niveles de protección de los usuarios de Fast-PPP, tal como se ha demostrado con figuras de mérito similares a las utilizadas en la aviación civil (los diagramas de Stanford).La tercera contribución de esta Tesis Doctoral ha sido la caracterización de la exactitud de los modelos ionosféricos utilizados actualmente en GNSS. El método usa medidas de fase, sin ambigüedad y sin diferenciar, gracias a la capacidad de modelado centimétrico empleado en la técnica de Fast-PPP. No solo los errores de los modelos de la ionosfera han sido cuantificados en términos absolutos y relativos, sino también, su efecto sobre la navegación.

Precise point positioning (PPP) is a technique for processing Global Navi- gation Satellite Systems (GNSS) data, often using recursive estimation methods e.g. a Kalman Filter, that can achieve centimetric accuracies using a single receiver. PPP is now the dominant real-time application in o shore marine positioning industry. For high precision real-time applications it is necessary to use high rate orbit and clock corrections in addition to high rate observations. As Kalman filters require input of process and measurement noise statistics, not precisely known in practice, the filter is non-optimal. Geodetic quality control procedures as developed by Baarda in the 1960s are well established and their extension to GNSS is mature. This methodology, largely unchanged since the 1990s, is now being applied to processing techniques that estimate more parameters and utilise many more observations at higher rates. \Detection, Identification and Adaption" (DIA), developed from an optimal filter perspective and utilising Baarda's methodology, is a widely adopted GNSS quality control procedure. DIA utilises various test statistics, which require observation residuals and their variances. Correct derivation of the local test statistic requires residuals at a given epoch to be uncorrelated with those from previous epochs. It is shown that for a non-optimal filter the autocorrelations between observations at successive epochs are non-zero which has implications for proper application of DIA. Whilst less problematic for longer data sampling periods, high rate data using real-time PPP results in significant time correlations between residuals over short periods. It is possible to model time correlations in the residuals as an autoregressive process. Using the autoregressive parameters, the effect of time correlation in the residuals can be removed, creating so-called whitened residuals and their variances. Thus a whitened test statistic can be formed, that satisfies the preferred assumption of uncorrelated residuals over time. The effectiveness of this whitened test statistic and its impact on quality control is evaluated.

Over the last few years, there has been a rising demand for sub-metre accuracy (and higher) for navigation and surveying using signals from Global Navigation Satellite Systems (GNSS). To meet this rising demand, many precise positioning techniques and algorithms using the carrier-phase observable have been developed. Currently, high accuracy Real-Time Kinematic (RTK) positioning is possible using relative or differential techniques which require one GNSS user receiver and at least one other as the reference (known) station within a certain distance from the user. Unlike these conventional differential positioning techniques, Precise Point Positioning (PPP) is based on processing carrier phase observations from only one GNSS receiver. This is more cost-effective as it removes the need for reference receivers and therefore, is not limited by baseline length. However, errors mitigated by ‘differencing’ in conventional methods must be modelled accurately and reliably for PPP. This thesis develops a PPP software platform in Matlab code and uses it to investigate the state-of-the-art PPP algorithms and develop enhancements. Specifically, it is well documented that conventional PPP algorithms suffer from long convergence periods ranging from thirty minutes (for static users) to hours (for dynamic users). Therefore, to achieve fast convergence, two approaches are developed in this thesis. Firstly, a combination of the state-of-the-art GNSS error models and new algorithms for measurement weighting, management of receiver clock jumps and assignment of a dynamic covariance factor, are exploited. Secondly, based on the results of the analysis of the quantitative relationships between the PPP convergence and each of the residual measurement noise level and satellite geometry, a strategy for the selection of satellites (GPS and GALILEO) for PPP is developed and exploited. Tests using 24 hours of real data show that the two developments above contribute to the realisation of static PPP positioning accuracies of 40 cm (3D, 100%) within a convergence time of 20 minutes. Furthermore, based on simulated data, the same accuracy is achieved in kinematic mode but within a convergence time of one hour. These levels of performance represent significant improvements over the state-of-the-art (i.e. convergence time of twenty minutes instead of thirty for static users and one hour instead of hours for dynamic users). The potential of the use of multiple frequencies from modernised GPS and GALILEO on float ambiguity PPP is demonstrated with simulated data, and shown to have the potential to offer significant improvement in the availability of PPP in difficult user environments such as urban areas. Finally, the thesis addresses the potential application of PPP for mission (e.g. safety critical) applications and the need for integrity monitoring. An existing Carrier-phase Receiver Autonomous Integrity Monitoring (CRAIM) algorithm is implemented and shown to have the potential to protect PPP users against abnormally large errors.

Different Global Navigation Satellite System (GNSS) constellations are available these days. This has led to an increase in the number of satellites available for the user, and that presents different performance levels for the user requirements like accuracy and convergence time. However, these benefits come from different constellations that have different reference times and for some, different frequencies. At the same time, the Precise Point Positioning (PPP) has also been presented as being a position solution within a certain level of accuracy and precision. Therefore, it is important to investigate the potential benefits from the PPP with a view to using a single or multi-constellation. These investigations include accuracy, precision, and convergence time. In addition, it is important to look at the individual performance of these constellations regarding the above improvements. This will give a clear decision about adopting a single or multi-constellation. It will also provide an independent solution, for instance for the station coordinates and troposphere, and independent estimated station velocities, without additional cost. This research has been conducted in three stages. Firstly, the research begins with an evaluation of the GPS and the GLONASS (GLO) constellation geometry using a new approach for computing the cumulative dilution of precision (DOP) rather than the conventional DOP which was found to be latitude-dependent. Then it investigates the achievable station coordinate accuracy from PPP scenarios for static positioning after choosing the most appropriate PPP strategy that needs to be followed. Furthermore, the effect of different precise products (satellite orbits and clocks) on the PPP solutions and the difference between those products has been covered. It has been proven that PPP solutions can reach the same precision as a Global Double-Difference (GDD) GPS solution. Most importantly, the PPP GLO is found to be capable of producing similar precision and accuracy when compared to PPP GPS as well as the GDD GPS solution. Secondly, this research also investigates the conventional strategy (using a model for the hydrostatic component and estimating the wet component) for estimating the troposphere Zenith Total Delay (ZTD) from the PPP solutions with an evaluation of the obtained accuracy of the tropospheric ZTD from four tropospheric models. It also presents an alternative strategy (estimating both components using different mapping functions and different process noises) for estimating the tropospheric ZTD from the PPP that can give millimeters of ZTD accuracy without affecting the station coordinate estimation and without relying on any metrological data or models. Validations have been conducted for the new strategy using PPP GPS, PPP GLO and PPP GPS+GLO. Regional validation was conducted over seven consecutive days for seven weeks, using the Ordnance Survey of Great Britain (OSGB) stations in the UK, and long-term (over one year) validation was conducted using 22 stations from the OSGB. The regional and long-term validations have been conducted using three different final precise products (satellite orbits (SP3) and clocks (CLK)), which are the EMX, ESA and GFZ. A global validation using ~76 IGS stations was conducted over a different period. This was conducted in three stages, using the final EMX, final IGS and real-time IGS precise products. It was found that this approach can be used in real-time as well as in post processing without a significant difference between the results. Finally, this research has investigated the potential of using the PPP GLO for crustal motion separate to using the PPP GPS. Consistent horizontal station rates were found between PPP GPS and GDD GPS solutions. It was also concluded that it should be possible to use the PPP GLO for crustal motion, as an independent and precise solution. However, there was a bias in the orientation components of the estimated horizontal station rates between the PPP GLO and both other solutions (PPP GPS and GDD GPS), which was concluded to be a system bias rather than a strategy bias.

Laser altimetry and satellite gravity surveys indicate that the St Elias Icefields are currently losing mass and are among the largest non-polar sea level contributors in the world. However, a poor understanding of glacier dynamics in the region is a major hurdle in evaluating regional variations in ice motion and the relationship between changing surface conditions and ice flux. This study combines in-situ dGPS measurements and advanced Radarsat-2 (RS-2) processing techniques to determine daily and seasonal ice velocities for the Kaskawulsh Glacier from summer 2009 to summer 2011. Three permanent dGPS stations were installed along the centreline of the glacier in 2009, with an additional permanent station on the South Arm in 2010. The Precise Point Positioning (PPP) method is used to process the dGPS data using high accuracy orbital reconstruction. RS-2 imagery was acquired on a 24-day cycle from January to March 2010, and from October to March 2010-2011 in a combination of ultra-fine and fine beam modes. Seasonal velocity regimes are readily identifiable in the dGPS results, with distinct variations in both horizontal velocity and vertical motion. The Spring Regime consists of an annual peak in horizontal velocity that corresponds closely with the onset of the melt season and progresses up-glacier, following the onset of melt at each station. The Summer Regime sees variable horizontal velocity and vertical uplift, superimposed on a long-term decline in motion. The Fall Regime sees a gradual slowing at all stations with little variation in horizontal velocity or vertical position. Rapid but short accelerations lasting up to 10 days were seen in the Winter regimes in both 2010 and 2011, occurring at various times throughout each regime. These events initiated at the Upper Station and progress down-glacier at propagation speeds up to 16,380 m day-1 and were accompanied by vertical uplift lasting for similar periods. Three velocity maps, one from the winter of 2010 and two from the fall/winter of 2011, produced from speckle tracking were validated by comparison with dGPS velocity, surface flow direction, and bedrock areas of zero motion, with an average velocity error of 2.0% and average difference in orientation of 4.3º.

Lo scopo di questo lavoro è sperimentare l’impiego di ricevitori a basso costo per il posizionamento di cicli in ambito urbano. Questo tipo di rilievo trova ampio impiego nello studio e verifica delle funzionalità del reticolo delle piste ciclabili. Il rilievo effettuato in condizioni di scarsa visibilità verso la costellazione satellitare e in presenza di riflessioni multiple indotte da superfici verticali, quali quelle degli edifici in ambito urbano, risulta affetto da specifiche problematiche che si è cercato di affrontare nella presente tesi. In particolare si è analizzato l’effetto del “multipath”, nel posizionamento GPS, di un ciclista in movimento su percorsi caratterizzati da “canyon urbano”, nel centrostorico di Bologna. La strumentazione sperimentata è consistita da un tablet Smasung Note 10.1, uno smartphone Samsung S4 e un ricevitore GNSS (U-blox Neo-7P) collegato ad una Raspberry Pi 2. Anche a livello software è stato sperimentato per le unità Samsung sia il software Strava, che il Blackcountry Navigator. Mentre l’acquisizione del sensore U-blox è avvenuta direttamente tramite connessione seriale in un file di testo. Nel primo capitolo verrà presentato il sistema GPS nella sua generalità. Nel secondo, invece, verrà descritta la parte del sistema GPS, che si è utilizzato per questo lavoro. Nel terzo si mostreranno gli strumenti e le apparecchiature utilizzate durante il lavoro. Nel quarto si procederà alla presentazione del caso di studio. Nell’ultimo capitolo verranno riportate le conclusioni di tutto il lavoro svolto.

Um método de posicionamento por GNSS (Global Navigation Satellite System) que vem se popularizando nos últimos anos é o Posicionamento por Ponto Preciso (PPP). Este método de posicionamento se utiliza de dados de apenas um receptor e requer, fundamentalmente, o uso de efemérides e correções dos relógios dos satélites precisos. O PPP nos últimos anos ganhou um impulso significativo em sua popularidade devido, principalmente, ao surgimento de serviços gratuitos de processamento on-line. Entre estes serviços on-line de processamento de PPP, destaca-se o fornecido pelo NRCan (Natural Resource Canada), denominado CSRS-PPP (Canadian Spatial Reference System – Precise Point Positioning). Nesta Tese utilizou-se o serviço canadense CSRS-PPP no processamento de um longo período de dados superior a onze anos coletados em noventa e cinco das estações da RBMC. A análise das velocidades obtidas a partir das respectivas séries temporais referentes às coordenadas diárias estimadas pelo CSRS-PPP bem como a determinação de suas coordenadas – através do PPP – referidas à época 2000.4, mostraram resultados com pequenas discrepâncias quando comparadas com os valores oficiais adotados para as estações analisadas. O problema detectado, refere-se à impossibilidade da adoção de velocidades lineares de translação no sistema cartesiano X, Y e Z, tendo em vista que na grande maioria das estações constatou-se um comportamento sazonal referente à altura elipsoidal, variação esta que afeta as translações em X, Y e Z ao longo do ano. Como solução, propõe-se a adoção das velocidades de deslocamento calculadas para coordenadas planas, particularmente as coordenadas UTM, sendo a altura elipsoidal corrigida através de modelos estabelecidos em função da variação sazonal registrada em cada uma das estações da RBMC.
A positioning method for GNSS (Global Navigation Satellite System) that has become more popular in recent years is the Precise Point Positioning (PPP). The PPP refers to the positioning method that utilizes data to only one receiver and requires fundamentally the use of ephemeris and corrections to the precise satellite clock. The PPP in recent years gained a significant boost in its popularity, mainly due to the emergence of free services online processing. Among these PPP processing on-line services, there is the one provided by NRCan (Natural Resource Canada) called CSRS-PPP (Canadian Spatial Reference System - Precise Point Positioning). In this Thesis used if the Canadian service CSRS-PPP to process data for a long period upper through eleven collected at ninety-five of RBMC stations. The analysis of the rates obtained from the respective time series relating to the daily coordinates estimated by the CSRS-PPP and the determination of its coordinates - through PPP - said at the time 2000.4, showed results with minor discrepancies compared with the official values adopted for the analyzed stations. The problem detected, refers to the impossibility of adopting linear translation speeds in the Cartesian system X, Y, and Z, considering that in most of the stations found a seasonal pattern related to the ellipsoidal height, this variation that affects translations in X, Y and Z throughout the year. As a solution, it is proposed the adoption of the forward speeds calculated for planar coordinates, particularly UTM coordinates, and the ellipsoid height corrected by established models depending on seasonal variations recorded in each of the stations RBMC.

[EN] Precise Point Positioning (PPP) method involves an absolute positioning technique from a single receiver with GNSS (Global Navigation Satellite Systems). Its theoretical basis consists of solving the position with observations using a single receiver, with clock and orbit state models, among other products. The main advance concerning the current differential technique is that differential or relative positioning uses the double-differences solution that requires, at least, two receivers to get a precise position or a receiver connected to a network of reference stations. However, until recently, and from a practical point of view, a precise absolute positioning with centimeter accuracy with a single GNSS receiver was considered unfeasible. The reason was the difficulty in cancellation of errors and the ambiguity resolution. The main factor that limits Precise Point Positioning (PPP) accuracy is the dependence on external information, which models the error sources, that is to say: the performance of the orbit and clock products, the quality of the observations, and the effects of the un-modeled or un-calibrated error sources. Precise ionospheric corrections and troposphere state models are also essential in order to improve positioning at centimeter level. Furthermore, in real-time PPP precise streams of products and state models are needed, and they must meet certain requirements of latency and continuous availability. In the case study of real-time positioning, the PPP technique is very sensible to gaps and outliers in the reception of the products and fluctuations in the constellation, producing lost of convergence, delay in initialization and a lack of accuracy in the results. Nowadays, this situation is changing, but it needs to evolve even more, because the real-time determination and the performance of the orbital parameters, clock states or other modeled errors of the GNSS satellites and signals, are still in a stage of improvement by the International GNSS Service, by the Analysis Centers and by researches all around the world. Therefore, the objective of this investigation was the study of Precise Point Positioning technique applied to the real-time case study, considering the performance of the available products in several sceneries and environments. The study focused on its application and how to improve limitations in the performance. The main tasks developed are: -A preliminary study of the multi - constellation context, the state of the art of Precise Point Positioning technique and modeling error sources, (chapters 1 and 2). -The review of the emission of the state models into a standard format and the discussion of the limitations in the alternatives in the generation of the models, (chapters 3 and 4). -The analysis of the optimization of this method with the development of new constellations, by means of the test of new products, and multiple simultaneous observations performed, (chapter 6). -To explore the possibilities of real-time recovering of integer ambiguities for PPP and the impact in the performance, providing practical demonstrations with experimental and standardized approaches, (chapter 7). -To study tactics to provide combined products in quasi-real time and real-time latency, (chapter 8), and in a regional or continental frame, with own applied solutions, (chapter 9). -The design and development of processing and analysis tools, (chapter 5), monitoring and distribution of results with the real-time PPP method, (chapter 10), and the study of potential applications, (chapter 11).
[ES] El método Precise Point Positioning, (PPP), consiste en una técnica de posicionamiento absoluto con un solo receptor GNSS (Global Navigation Satellite Systems). Su fundamento teórico se basa en resolver la posición con las observaciones de un único equipo, utilizando correcciones de osciladores y de órbitas de satélites, entre otros modelos. La potencia del método con respecto a la técnica diferencial reside en que el posicionamiento diferencial o relativo utiliza la solución de dobles diferencias que requiere, al menos, dos receptores para obtener una posición precisa o un receptor conectado a una red de estaciones de referencia. Sin embargo hasta hace poco y a efectos prácticos, un posicionamiento absoluto con precisión de centímetros con un solo equipo se ha considerado irrealizable. El motivo reside en la dificultad de la cancelación de errores y de obtener la resolución de ambigüedades enteras. El principal factor que limita, por tanto, el posicionamiento absoluto preciso es la dependencia de productos externos que modelen las fuentes de error, es decir: el rendimiento de los modelos de órbitas y relojes, la calidad de las observaciones, y los errores no modelados o no calibrados. Las correcciones ionosféricas y modelos de estado de la troposfera también son esenciales para alcanzar precisiones a nivel del centímetro. Por otro lado, si se trabaja con la técnica PPP en tiempo real, se necesita productos y modelos de estado recibidos continuamente a través de paquetes de datos por Internet, que deben cumplir con ciertos requisitos de latencia y disponibilidad continua. En el caso de estudio de posicionamiento en tiempo real, la técnica PPP es además muy sensible a las anomalías y las pérdidas en la recepción de los productos, y a las fluctuaciones de la constelación, produciendo pérdidas de convergencia, retrasos en la inicialización, y falta de continuidad y exactitud en los resultados. En este momento esta situación está experimentando grandes cambios, pero necesita evolucionar aún más, ya que la determinación en tiempo real y el rendimiento de los parámetros orbitales, estados de reloj u otros modelos de error de los satélites GNSS y sus señales, se encuentra todavía en fase de mejora por parte del International GNSS Service, por parte de los Centros de Análisis y por parte de investigadores de todo el mundo. Por lo tanto, el objetivo de este trabajo ha sido el estudio de la técnica de posicionamiento Precise Point Positioning enfocada al caso de tiempo real, en base al rendimiento de los productos disponibles en varios escenarios y entornos. El estudio se centró en su aplicación y en la implementación de soluciones para mejorar sus limitaciones. Las principales tareas desarrolladas son: -Un estudio preliminar del entorno multi-constelación, del estado del arte de la técnica Precise Point Positioning, así como de los errores a modelar, (capítulos 1 y 2). -La supervisión de la emisión de modelos en un formato estándar, y la discusión de las limitaciones existentes en las alternativas para su generación, (capítulos 3 y 4). -El análisis de la optimización de este método con el desarrollo de nuevas constelaciones, a través de la evaluación de nuevos productos y sesiones simultáneas de observación, (capítulo 6). -La exploración de las posibilidades de recuperación de la naturaleza entera de las ambigüedades y su repercusión en términos de rendimiento, proporcionando demostraciones reales, con aproximaciones experimentales y estandarizadas, (capítulo 7). -El estudio de las tácticas para proporcionar productos combinados robustos en tiempo quasi-real y real, (capítulo 8), y en un marco regional o continental, (capítulo 9), con soluciones propias aplicadas. -El diseño y desarrollo de herramientas de cálculo y apoyo, (capítulo 5), de monitorización y distribución de resultados procedentes de PPP en tiempo real, (capítulo 10), y el e
[CAT] El mètode Precise Point Positioning, (PPP), consisteix en una tècnica de posicionament absolut amb un sol receptor GNSS (Global Navigation Satellite Systems). El seu fonament teòric consisteix a resoldre la posició amb observacions d'un únic equip utilitzant correccions d'oscil¿ladors i d'òrbites de satèl¿lits, entre altres models. La potència del mètode respecte a la tècnica diferencial és que el posicionament diferencial o relatiu utilitza la solució de dobles diferències que requereix, almenys, dos receptors per a obtenir una posició precisa o un receptor connectat a una xarxa d'estacions de referència. No obstant això, fins fa poc i a efectes pràctics, un posicionament absolut amb precisió de centímetres amb un sol equip GNSS s'ha estat considerant irrealitzable. El motiu es troba en la dificultat de la cancel¿lació d'errors i d'obtenir la resolució d'ambigüitats senceres. El principal factor que limita, per tant, el posicionament absolut precís és la dependència de productes externs que modelen les fonts d'error, es a dir: el rendiment dels models d'òrbites i oscil¿ladors, la qualitat de les observacions, i els errors no modelats o no calibrats. Les correccions ionosfèriques i models d'estat de la troposfera també són essencials per a aconseguir precisions a nivell del centímetre amb un equip. D'altra banda, si es treballa amb la tècnica PPP en temps real, es necessita productes i models d'estat rebuts contínuament a través de paquets de dades per Internet, que han de complir amb certs requisits de latència i disponibilitat contínua. En el cas d'estudi de posicionament en temps real, la tècnica PPP és a més molt sensible a les anomalies i les pèrdues en la recepció dels productes, i a les fluctuacions de la constel¿lació, produint pèrdues de convergència, retards en la inicialització i falta de continuïtat i exactitud en els resultats. En aquest moment aquesta situació està experimentant grans canvis, però necessita evolucionar encara més, ja que la determinació en temps real i el rendiment dels paràmetres orbitals, els estats de rellotge o altres models d'error dels satèl¿lits GNSS i els seus senyals, es troben encara en fase de millora per part de l'International GNSS Service, per part dels Centres d'Anàlisi i per part d'investigadors de tot el món. Per tant, l'objectiu d'aquest treball ha consistit en l'estudi de la tècnica Precise Point Positioning enfocat al cas de temps real, fonamentat amb el rendiment dels productes disponibles a diversos escenaris i entorns. L'estudi es va centrar en la seva aplicació i en la implementació de solucions per millorar les limitacions en la seua productivitat. Les principals tasques desenvolupades són: -Un estudi preliminar de l'entorn multi-constel¿lació, l'estat de l'art de la tècnica Precise Point Positioning, així com dels errors a modelar, (capítols 1 i 2). -La supervisió de l'emissió de models amb un format estàndard, i la discussió de les limitacions en les alternatives a la generació de models, (capítols 3 i 4). -Anàlisi de l'optimització d'aquest mètode amb el desenvolupament de noves constel¿lacions, amb l'avaluació de nous productes i múltiples sessions simultànies d'observació, (capítol 6). -L'exploració de les possibilitats de recuperació de la naturalesa sencera de les ambigüitats i la seva repercussió en termes de rendiment, proporcionant demostracions reals, utilitzant aproximacions experimentals i estandarditzades, (capítol 7). -L'estudi de les tàctiques per a proporcionar productes combinats robustos en temps quasi-real i en temps real, (capítol 8), i en un marc regional o continental, amb solucions pròpies aplicades, (capítol 9). -El disseny i desenvolupament d'eines de càlcul i suport (capítol 5), de monitorització i distribució de resultats aplicats al cas de PPP en temps real, (capítol 10), i l'estudi de potencials aplicacions de la tècnica, (capí
Capilla Romá, R. (2015). Aportación al estudio de la capacidad de los modelos conceptuales en posicionamiento absoluto preciso (Precise Point Positioning) para tiempo real a través del análisis del rendimiento de productos y prototipos en un escenario multi-constelación GNSS [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/52814
TESIS

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Nesta dissertação investiga-se o Posicionamento por Ponto Preciso (PPP), nos modos estático e cinemático, utilizando o Filtro de Kalman Estendido. Foram corrigidos os erros devido aos efeitos da refração troposférica, relatividade, movimento de rotação da Terra, variações das marés terrestres, correção do centro de fase da antena do satélite e fase Wind- up. Os efeitos devido à ionosfera foram minimizados através da combinação linear Ion-Free. A perda de ciclo foi detectada através da combinação linear widelane, envolvendo as duas observáveis: fase da onda portadora e pseudodistância. Quando a perda de ciclo é detectada, uma nova ambigüidade é inicializada no lugar da antiga. As implementações foram realizadas no software FILTER_FCT, em desenvolvimento na FCT/UNESP, o qual processava apenas a pseudodistância. Visando mostrar a acurácia que pode ser obtida com o PPP, foram realizados três experimentos: PPP no modo estático, PPP estático simulando o modo cinemático e PPP cinemático. No primeiro e no segundo experimentos foram utilizados dados das estações GPS: PPTE, VICO, RIOD e FORT, pertencentes à Rede Brasileira de Monitoramento Contínuo (RBMC), e da estação FRDN, localizada em Fredericton, no Canadá. No terceiro experimento foram utilizados dados do receptor GPS a bordo do satélite CHAMP. No PPP estático, utilizou-se como estratégia de processamento a modificação da variância das coordenadas e do relógio do receptor na matriz de variância-covariância do Filtro de Kalman Estendido. Verificou-se uma discrepância em relação às coordenadas consideradas verdadeiras na ordem de decímetros, com exceção das estações VICO e RIOD, que foram da ordem de centímetros.
In this dissertation the Precise Point Positioning (PPP), in static and kinematic modes, using Extended Kalman Filter is investigated. The errors due to troposphere refraction, relativity, movement of Earth's rotation, tide loading, satellite antenna phase center offset and phase wind-up were corrected. The effects due to ionosphere were minimized through the Ionospheric-Free linear combination. The widelane combination, involving phase and pseduorange, was used to detect cycle slips. When a cycle slip is detected, a new ambiguity is initialized in the place of the old one. The implementations were accomplished in the FILTER_FCT software. To show the accuracy in the PPP, three experiments were accomplished: PPP in the static mode, PPP in the static mode simulating the kinematic mode and PPP in kinematic mode. In the first and second experiments, data from PPTE, VICO, RIOD and FORT stations belonging to Brazilian Network for Continuous Monitoring (RBMC), and FRDN station located in Fredericton, Canada, were used. In the third experiment data from a GPS receiver on board of the CHAMP satellite were used. In static PPP, the modification of the coordinates variance and the receiver clock was used as processing strategy. The discrepanc ies obtained in the static positioning were on the order of decimeters, except for VICO and RIOD stations where they were on the order of centimeters. When the clock receiver variance was increased from (3.300)ø mø to (10.000)ø mø , the values of the discrepancies also increased, on the order of centimeters. Then, there is influence of the receiver clock variance in the estimated coordinates. The residual part of the tropospheric effects was estimated with the introduction of a scale factor in the processing.

The thesis deals with processing of epoch-wise GNSS measurements from local geodynamic network Sněžník. Its aim is to evaluate the geodynamics in the area of Králický Sněžník Massif and to assess the capabilities of epoch-wise GNSS measurements to detect the geodynamic movements. Within the thesis the comprehensive processing of all the GNSS measurements observed between years 1997 and 2011 is realized using the reprocessed products of first IGS reprocessing Repro1. Bernese GPS software version 5.0 is used for all the processing.

Orientador: João Frnacisco Galera Monico
Banca: Paulo de Oliveira Camargo
Banca: Leonardo Castro de Oliveira
Nesta dissertação investiga-se o Posicionamento por Ponto Preciso (PPP), nos modos estático e cinemático, utilizando o Filtro de Kalman Estendido. Foram corrigidos os erros devido aos efeitos da refração troposférica, relatividade, movimento de rotação da Terra, variações das marés terrestres, correção do centro de fase da antena do satélite e fase Wind- up. Os efeitos devido à ionosfera foram minimizados através da combinação linear Ion-Free. A perda de ciclo foi detectada através da combinação linear widelane, envolvendo as duas observáveis: fase da onda portadora e pseudodistância. Quando a perda de ciclo é detectada, uma nova ambigüidade é inicializada no lugar da antiga. As implementações foram realizadas no software FILTER_FCT, em desenvolvimento na FCT/UNESP, o qual processava apenas a pseudodistância. Visando mostrar a acurácia que pode ser obtida com o PPP, foram realizados três experimentos: PPP no modo estático, PPP estático simulando o modo cinemático e PPP cinemático. No primeiro e no segundo experimentos foram utilizados dados das estações GPS: PPTE, VICO, RIOD e FORT, pertencentes à Rede Brasileira de Monitoramento Contínuo (RBMC), e da estação FRDN, localizada em Fredericton, no Canadá. No terceiro experimento foram utilizados dados do receptor GPS a bordo do satélite CHAMP. No PPP estático, utilizou-se como estratégia de processamento a modificação da variância das coordenadas e do relógio do receptor na matriz de variância-covariância do Filtro de Kalman Estendido. Verificou-se uma discrepância em relação às coordenadas consideradas verdadeiras na ordem de decímetros, com exceção das estações VICO e RIOD, que foram da ordem de centímetros.
In this dissertation the Precise Point Positioning (PPP), in static and kinematic modes, using Extended Kalman Filter is investigated. The errors due to troposphere refraction, relativity, movement of Earth's rotation, tide loading, satellite antenna phase center offset and phase wind-up were corrected. The effects due to ionosphere were minimized through the Ionospheric-Free linear combination. The widelane combination, involving phase and pseduorange, was used to detect cycle slips. When a cycle slip is detected, a new ambiguity is initialized in the place of the old one. The implementations were accomplished in the FILTER_FCT software. To show the accuracy in the PPP, three experiments were accomplished: PPP in the static mode, PPP in the static mode simulating the kinematic mode and PPP in kinematic mode. In the first and second experiments, data from PPTE, VICO, RIOD and FORT stations belonging to Brazilian Network for Continuous Monitoring (RBMC), and FRDN station located in Fredericton, Canada, were used. In the third experiment data from a GPS receiver on board of the CHAMP satellite were used. In static PPP, the modification of the coordinates variance and the receiver clock was used as processing strategy. The discrepanc ies obtained in the static positioning were on the order of decimeters, except for VICO and RIOD stations where they were on the order of centimeters. When the clock receiver variance was increased from (3.300)ø mø to (10.000)ø mø , the values of the discrepancies also increased, on the order of centimeters. Then, there is influence of the receiver clock variance in the estimated coordinates. The residual part of the tropospheric effects was estimated with the introduction of a scale factor in the processing.
Mestre

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Atulim (2002) and Racanicchi (2003) had planned and implemented a geodetic GPS network in São Carlos city, which needed maintenance and revision. The proposals of this dissertation had consisted of: i) to bring up to date the GPS geodetic network in the city of São Carlos and to make it compatible with the SIRGAS2000 (Geocentric Reference System of Americas 2000), with new network adjustment and injunction in two geodesic vertices in the urban area of São Carlos, homologated by the IBGE after the implantation of the original geodetic network in 2003; ii) to evaluate and to compare the new results of the geodetic network coordinates obtained with the relative positioning through the tracking of artificial satellites, according to technology NAVSTAR/GPS and adjusted through the Least Squares Method, with results of coordinates obtained through the Precise Point Positioning (PPP) Method, processed by PPP on-line services. Analyzing the results obtained in this dissertation, it was possible to evaluate that the application of PPP Method, since that followed the specific orientations of each on-line service used, takes care perfectly to the required to support of cadastral registry and location services for the most varied purposes, however it does not substitute yet other services that demand highest degree of accuracy only obtained with vectors and network adjustment with statistical control of processes that demand high computational activity.
Atulim (2002) e Racanicchi (2003) planejaram e implantaram uma rede geodésica GPS no município de São Carlos, que necessitou de manutenção e revisão. As propostas desta dissertação consistiram em: i) atualizar a rede geodésica GPS no município de São Carlos e compatibilizá-la com o SIRGAS2000 (Sistema de Referência Geocêntrica das Américas 2000), com novo ajustamento da rede geodésica e injuncionamento em dois vértices geodésicos na área urbana de São Carlos, homologados pelo IBGE após a implantação da rede geodésica original; ii) avaliar e comparar os novos resultados das coordenadas da rede geodésica de São Carlos obtidas com posicionamento relativo através do rastreamento de satélites artificiais, segundo a tecnologia NAVSTAR/GPS (Navigation Satellite Timing and Ranging/Global Positioning System) e ajustadas através do Método dos Mínimos Quadrados (MMQ), com os resultados das coordenadas obtidas através do Método de Posicionamento Pontual Preciso (PPP), processadas por serviços de cálculo de PPP on-line. Analisando os resultados obtidos nesta dissertação, foi possível avaliar que a aplicação do Método PPP, desde que seguidas as orientações específicas de cada serviço on-line utilizado, atende perfeitamente à exigência requerida para apoiar serviços de cadastro e locação para as mais variadas finalidades, porém não substitui ainda outros serviços que demandam alto grau de exatidão conseguidas somente com vetores e ajustamento de rede com controle estatístico de processos que demandam alta atividade computacional.

Accurate positioning is very important in many various applications. Today one of the mostused methods for this is DGPS, i.e. relative positioning. DGPS can be extended to aWADGPS (Wide Area DGPS) which consists of a network of reference stations which covera whole region, country or continent. This implies that you are dependent on other factors outof control of the user, and that a connection to the reference stations is needed.Precise point positioning, PPP, is an absolute positioning method where no reference stationsare involved. Ordinary single point positioning is based on broadcast ephemeris, and theaccuracy is on the 15m level. Per definition PPP is based on precise ephemeris, with muchhigher accuracy in the orbital parameters and in the satellite clock information. The resultshould therefore be more accurate. Precise ephemeris are available in different levels ofaccuracies (final, rapid and ultra-rapid) and can be downloaded from the internet for free.Precise clock files are not available as ultra-rapid and therefore it is not possible to getaccurate PPP-solutions in real-time.In Sweden there are several networks for relative positioning, e.g. through SWEPOS orEPOS. This might not be the case in other areas. As accurate PPP-solutions are not availablein real-time, PPP could be used to establish a reference station for DGPS/RTK for real-timemeasurements in those areasThe objective of this research is to evaluate precise point positioning regarding accuracy.Observation files from both IGS and SWEPOS-stations have been used in order to find out ifyou can expect the same accuracy wherever you are on earth. A couple of points have alsobeen measured only for this investigation in order to find out if the result will be the sameunder ordinary conditions. Coordinates of each point are determined with different duration ofobservation times and different level of accuracy of the ephemeris (final, rapid and ultrarapid).Bernese 5.0 and Auto-Gipsy have been used to compute the PPP-solutions and thenthe result is compared with the true position. The self-measured points are also determinedwith a WADGPS (Omnistar) in order to easily be able to compare PPP with a traditionalmethod.As expected the result becomes better for longer observation times and with higher accuracyof the ephemeris. The difference in accuracy between using rapid and final ephemeris is sosmall that it can be neglected in most applications. In almost all cases the accuracy is betterthan 10cm after only one hour of observations with rapid ephemeris. The investigation doesnot indicate significantly differences in accuracy depending on latitude and differencesbetween the self-measured points and IGS- and SWEPOS-stations can also be neglected.Using rapid or final ephemeris, the PPP-derived coordinates are much more accurate than theones obtained with Omnistar.
Noggrann positionsbestämning med hjälp av GPS har flera olika tillämpningar. En utav depopuläraste metoderna idag är DGPS, dvs. relativ positionering. WADGPS (Wide AreaDGPS) är ett nätverk av referensstationer som täcker ett större område så som ett land eller enkontinent. Detta innebär att en användare är beroende av faktorer som ligger utanför hanskontroll och av att det finns en kommunikationslänk till referensstationerna.Precise point positioning, PPP, är en absolut positioneringsmetod där inga referensstationerdeltar i beräkningarna. Vanlig enkelpunktsbestämning bygger på de bandata som kommermed satellitmeddelandet och noggrannheten ligger i allmänhet omkring 15m. PPP baseras perdefinition på precis efemerider med mycket bättre noggrannhet i bandata och satelliternasklockinformation. Resultatet bör därför bli avsevärt mycket bättre. Precisa efemerider finns iolika noggrannhetsnivåer (final, rapid och ultra-rapid) och kan laddas ner gratis från internet.Precis information om satelliternas klockor kommer inte med ultra-rapid efemerider varför detinte går att få noggranna lösningar med PPP i realtid.I Sverige finns väl utvecklade nät för relativpositionering, tex. SWEPOS eller EPOS. Så ärkanske inte fallet i andra delar av världen. Med PPP skulle man kunna etablera egnareferenspunkter och på så sätt kunna mäta i realtid med DGPS.Målet med detta examensarbete är att undersöka vilken noggrannhet som kan uppnås medPPP. Observationsfiler från både SWEPOS- och IGS-stationer har använts för att se om mankan förvänta sig samma resultat oberoende av var på jorden man befinner sig. Även någrapunkter har mätts enbart för denna undersökning för att se om resultatet blir detsamma undervanliga förhållanden. Koordinaterna för varje punkt har beräknats med olika observationstideroch olika typer av efemerider (final, rapid och ultra-rapid). Bernese 5.0 och Auto-Gipsy haranvänts för att beräkna PPP-koordinaterna, som sedan har jämförts med de sanna värdena.Egna mätta punkter har även bestämts med WADGPS (Omnistar) för att enkelt kunna jämföraPPP med en traditionell metod.Som väntat blev resultatet bättre för längre observationstider och för noggrannare efemerider.Skillnaderna i noggrannhet mellan final och rapid efemerider är så liten att den kan bortsesifrån i de flesta fall. Bortsett från något undantag är noggrannheten bättre än 10cm efter baraen timmes mätning med rapid efemerider. Undersökningen visar inte någon signifikantskillnad i noggrannhet beroende på latitud, och skillnaden mellan de egna mätta punkternaoch IGS- och SWEPOS-stationer kan också försummas. Koordinater beräknade med PPP,beräknade med rapid och final efemerider är mycket mer noggranna än de som beräknats medOmnistar.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
As redes ativas GPS tem se tornando cada vez mais utilizadas nos levantamentos geodésicos. As estações que fazem parte dessas redes têm suas coordenadas determinadas com alta precisão que, devido à estabilidade na sua construção e disponibilidade de dados, são chamadas estações de referência. Os dados podem ser empregados numa diversidade de pesquisas e projetos, sendo um dos mais comuns atualmente os de levantamentos geodésicos. O estudo e monitoramento do vapor d’água na atmosfera e movimento de placas litosféricas são exemplos de aplicações. Dentre os métodos de posicionamento GPS, o Posicionamento por Ponto Preciso (PPP) vem apresentando resultados muito promissores. Uma característica do PPP está relacionada com a modelagem e/ou estimação de todos os erros envolvidos nesse método. A acurácia obtida para as coordenadas pode ser da ordem de poucos milímetros, tal como no método de posicionamento relativo. Efeitos sazonais podem afetar esta acurácia caso não sejam considerados. Desta forma, é desejável dispor do conhecimento de todos os fatores sazonais (movimento do pólo, marés terrestres e cargas oceânicas) que interferem na posição da estação, visando minimizá-los ou modelá-los. Contudo, há evidências da existência de outros efeitos dessa natureza ainda não levados em consideração no PPP. Nesta pesquisa, foram realizados alguns experimentos com a finalidade de investigar os efeitos sazonais presentes nas séries temporais das coordenadas das estações Brasília (BRAZ), Euzébio (BRFT) e Manaus (NAUS) pertencentes à Rede Brasileira de Monitoramento Contínuo (RBMC)...
The active GPS networks have being more and more used in the geodetic surveying. The stations that belong to these networks have the coordinates determined with high precision, due to the construction stability and data availability, so they are called reference stations. The reference station data can be employed in a diversity of researches, where the geodetic positioning is one of the most common. The study and monitoring of the water vapor in the atmosphere and the lithosphere plates movement are examples of applications. Among the existent methods of GPS positioning, the Precise Point Positioning (PPP) has been presented great results. The accuracy obtained for the coordinates can reaches few millimeters, such as in the relative positioning. An important aspect concerning PPP is related to the modeling and / or estimation of all errors that affect this method. Among the errors, the seasonal effects can affect PPP accuracy if they are not considered. In this way, it is desirable to take care of all the seasonal factors (polar motion, solid tides and ocean loading) that interfere in the station position, aiming to minimize or to model them. Besides, there are evidences of other seasonal effects that still remain in PPP. In this research, some experiments were carried out with the finality of investigating the seasonal effects in the coordinate time series of the stations Brasília (BRAZ), Euzébio (BRFT) and Manaus (NAUS), that belong to the Rede Brasileira de Monitoramento Contínuo (RBMC). The coordinates of these stations were estimated daily using... (Complete abstract click electronic access below)

Resumo: As redes ativas GPS tem se tornando cada vez mais utilizadas nos levantamentos geodésicos. As estações que fazem parte dessas redes têm suas coordenadas determinadas com alta precisão que, devido à estabilidade na sua construção e disponibilidade de dados, são chamadas estações de referência. Os dados podem ser empregados numa diversidade de pesquisas e projetos, sendo um dos mais comuns atualmente os de levantamentos geodésicos. O estudo e monitoramento do vapor d'água na atmosfera e movimento de placas litosféricas são exemplos de aplicações. Dentre os métodos de posicionamento GPS, o Posicionamento por Ponto Preciso (PPP) vem apresentando resultados muito promissores. Uma característica do PPP está relacionada com a modelagem e/ou estimação de todos os erros envolvidos nesse método. A acurácia obtida para as coordenadas pode ser da ordem de poucos milímetros, tal como no método de posicionamento relativo. Efeitos sazonais podem afetar esta acurácia caso não sejam considerados. Desta forma, é desejável dispor do conhecimento de todos os fatores sazonais (movimento do pólo, marés terrestres e cargas oceânicas) que interferem na posição da estação, visando minimizá-los ou modelá-los. Contudo, há evidências da existência de outros efeitos dessa natureza ainda não levados em consideração no PPP. Nesta pesquisa, foram realizados alguns experimentos com a finalidade de investigar os efeitos sazonais presentes nas séries temporais das coordenadas das estações Brasília (BRAZ), Euzébio (BRFT) e Manaus (NAUS) pertencentes à Rede Brasileira de Monitoramento Contínuo (RBMC)... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The active GPS networks have being more and more used in the geodetic surveying. The stations that belong to these networks have the coordinates determined with high precision, due to the construction stability and data availability, so they are called reference stations. The reference station data can be employed in a diversity of researches, where the geodetic positioning is one of the most common. The study and monitoring of the water vapor in the atmosphere and the lithosphere plates movement are examples of applications. Among the existent methods of GPS positioning, the Precise Point Positioning (PPP) has been presented great results. The accuracy obtained for the coordinates can reaches few millimeters, such as in the relative positioning. An important aspect concerning PPP is related to the modeling and / or estimation of all errors that affect this method. Among the errors, the seasonal effects can affect PPP accuracy if they are not considered. In this way, it is desirable to take care of all the seasonal factors (polar motion, solid tides and ocean loading) that interfere in the station position, aiming to minimize or to model them. Besides, there are evidences of other seasonal effects that still remain in PPP. In this research, some experiments were carried out with the finality of investigating the seasonal effects in the coordinate time series of the stations Brasília (BRAZ), Euzébio (BRFT) and Manaus (NAUS), that belong to the Rede Brasileira de Monitoramento Contínuo (RBMC). The coordinates of these stations were estimated daily using... (Complete abstract click electronic access below)
Orientador: João Francisco Galera Monico
Coorientador: João Carlos Chaves
Banca: Marcelo Tomio Matsuoka
Banca: Ailton Pagamisse
Mestre

A new method of adaptive impulse control is developed to precisely and quickly control the position of machine components subject to friction. Friction dominates the forces affecting fine positioning dynamics. Friction can depend on payload, velocity, step size, path, initial position, temperature, and other variables. Control problems such as steady-state error and limit cycles often arise when applying conventional control techniques to the position control problem. Studies in the last few decades have shown that impulsive control can produce repeatable displacements as small as ten nanometers without limit cycles or steady-state error in machines subject to dry sliding friction. These displacements are achieved through the application of short duration, high intensity pulses. The relationship between pulse duration and displacement is seldom a simple function. The most dependable practical methods for control are self-tuning; they learn from online experience by adapting an internal control parameter until precise position control is achieved. To date, the best known adaptive pulse control methods adapt a single control parameter. While effective, the single parameter methods suffer from sub-optimal settling times and poor parameter convergence. To improve performance while maintaining the capacity for ultimate precision, a new control method referred to as Adaptive Impulse Control (AIC) has been developed. To better fit the nonlinear relationship between pulses and displacements, AIC adaptively tunes a set of parameters. Each parameter affects a different range of displacements. Online updates depend on the residual control error following each pulse, an estimate of pulse sensitivity, and a learning gain. After an update is calculated, it is distributed among the parameters that were used to calculate the most recent pulse. As the stored relationship converges to the actual relationship of the machine, pulses become more accurate and fewer pulses are needed to reach each desired destination. When fewer pulses are needed, settling time improves and efficiency increases. AIC is experimentally compared to conventional PID control and other adaptive pulse control methods on a rotary system with a position measurement resolution of 16000 encoder counts per revolution of the load wheel. The friction in the test system is nonlinear and irregular with a position dependent break-away torque that varies by a factor of more than 1.8 to 1. AIC is shown to improve settling times by as much as a factor of two when compared to other adaptive pulse control methods while maintaining precise control tolerances.

碩士
國立成功大學
測量及空間資訊學系碩博士班
97
The GPS buoy is a floating buoy equipped with a geodetic-grade dual-frequency GPS receiver and has been demonstrated to effectively and economically collect sea level data. In order to eliminate the systematic errors of GPS buoy, traditional DGPS (Differential Global Positioning System) techniques is used to provide positional information of GPS buoy, thus an additional GPS receiver is required to set up as a reference station. Because International GNSS Service (IGS) recently provides the precise ephemeris and the corrections of satellites clock, a novel technique, Precise Point Positioning (PPP), is developed to compute a station’s coordinate with acceptable accuracy where its 3D RMSE in kinematic and static modes are smaller than 1 meter and 1 decimeter, respectively by using only one GPS receiver to reduce labor and expense and simplify the data processing scheme. In this study, six campaigns around Anping tide gauge, Tainan, were successfully performed and the collected GPS buoy data were processed with four types of precise ephemeris provided by IGS, including final product, rapid product, ultra-rapid product (observed half) and ultra-rapid product (predicted half) with the use of PPP technique. Comparing the PPP results with DGPS, the differences reach 3~5 cm in the horizontal and 10 cm in the vertical with final product; 6~8 cm in the horizontal and 15 cm in the vertical with rapid product; 15~20 cm in the horizontal and 30~40 cm in the vertical with ultra-rapid product (observed half); 2~3 m in the horizontal and 3~4 m in the vertical with ultra-rapid product (predicted half). In addition, the collected data were also processed by DGPS techniques using different reference stations to analyze the effect of various baselines. The results show that accuracy degrades when the baselines increase. Finally, in additional to the comparison of results derived by PPP and DGPS, they were all compared to Anping tide gauge records as well. The aim of this study is the analysis of height variations provided by different methodologies. Comparing to Anping tide gauge records, the differences in height variations can achieve 4.5 cm with DGPS; 6 cm with final product; 10 cm with rapid product; 25 cm with ultra-rapid product (observed half); 1~2 m with ultra-rapid product (predicted half).

Precise Point Positioning (PPP) ermöglicht eine präzise Positionsbestimmung mittels globaler Satellitennavigationssysteme (Global Navigation Satellite System, GNSS) ohne die direkte Verwendung der Beobachtungsdaten von regionalen Referenzstationen. Die wesentlichste Einschränkung von PPP im Vergleich zu differenziellen Auswertetechniken (Real-Time Kinematic, RTK) ist die deutlich längere Konvergenzzeit. Voraussetzung für die Verkürzung der Konvergenzzeit ist die Festsetzung der geschätzten Mehrdeutigkeiten auf ganzzahlige Werte. Die Mehrdeutigkeitslösung verlangt ein robustes funktionales Modell und beruht auf einem zweistufigen Mehrdeutigkeitsfestsetzungsverfahren, welches frei von ionosphärischen Einflüssen 1. Ordnung ist. Die sowohl auf Code- als auch auf Phasenbeobachtungen basierende Melbourne-Wübbena-Linearkombination erlaubt hierbei eine einfache Festsetzung der Widelane-Mehrdeutigkeiten. Infolgedessen kann zur Berechnung der ionosphären-freien Linearkombination die im Vergleich zur Wellenlänge der ionosphären-freien Linearkombination deutlich größere Narrowlane-Wellenlänge verwendet werden. Zur Stabilisierung des im Normalfall lediglich auf den Beobachtungsdaten des amerikanischen Global Positioning System (GPS) beruhenden funktionalen Modells können die Beobachtungsdaten des russischen GLObal’naya NAvigatsioannaya Sputnikovaya Sistema (GLONASS) beitragen. Aufgrund der Technik, die GLONASS zur Identifizierung der einzelnen Satelliten einsetzt (Frequency Division Multiple Access, FDMA), unterscheiden sich die Frequenzen der einzelnen Satelliten. Die leicht unterschiedlichen Frequenzen erschweren die Modellierung und Korrektion der instrumentell bedingten Signalverzögerungen (z. B. Fractional-Cycle Biases (FCB)). Vor diesem Hintergrund kann das konventionelle Mehrdeutigkeitsfestsetzungsverfahren nur bedingt für GLONASS verwendet werden. Die Untersuchung der instrumentell bedingten GLONASS-Signalverzögerungen sowie die Entwicklung einer alternativen Methode zur Festsetzung der GLONASS-Mehrdeutigkeiten mit dem Ziel einer kombinierten GPS/GLONASS-Mehrdeutigkeitslösung sind die Schwerpunkte der vorliegenden Arbeit. Die entwickelte alternative Mehrdeutigkeitsfestsetzungsstrategie baut auf der puren Widelane-Linearkombination auf, weshalb globale Ionosphärenmodelle unabdingbar sind. Sie eignet sich sowohl für GLONASS als auch für GPS und zeigt gleichwertige Ergebnisse für beide GNSS, wenngleich im Vergleich zur konventionellen Methode mit geringeren Mehrdeutigkeitsfestsetzungsquoten zu rechnen ist.
Precise Point Positioning (PPP) allows for accurate Global Navigation Satellite System (GNSS) based positioning without the immediate need for observations collected by regional station networks. The fundamental drawback of PPP in comparison to differential techniques such as Real-Time Kinematic (RTK) is a significant increase in convergence time. Among a plurality of different measures aiming for a reduction of convergence time, fixing the estimated carrier phase ambiguities to integer values is the key technique for success. The ambiguity resolution asks for a robust functional model and rests upon a two-stage method ruling out first-order ionospheric effects. In this context the Melbourne-Wübbena linear combination of dual-frequency carrier phase and code measurements leverages a simple resolution of widelane ambiguities. As a consequence the in comparison to the wavelength of the ionosphere-free linear combination significantly longer narrowlane wavelength can be used to form the ionosphere-free linear combination. By default the applied functional model is solely based on observations of the Global Positioning System (GPS). However measurements from the GLObal’naya NAvigatsioannaya Sputnikovaya Sistema (GLONASS) can contribute to improve the model’s stability significantly. Due to the technique used by GLONASS to distinguish individual satellites (Frequency Division Multiple Access, FDMA), the signals broadcast by those satellites differ in their frequencies. The resulting slightly different frequencies constitute a barricade for both modelling and correcting any device-dependent signal delays, e.g. fractional-cycle biases (FCB). These facts limit the applicability of the conventional ambiguity-fixing approach when it comes to GLONASS signals. The present work puts a focus both on investigating the device-dependent GLONASS signal delays and on developing an alternative method for fixing GLONASS ambiguities with the ultimate objective of a combined GPS/GLONASS ambiguity resolution. The alternative ambiguity resolution strategy is based on the pure widelane linear combination, for which reason ionospheric corrections are indispensable. The procedure is applicable for GLONASS in the first instance but reveals equivalent results for both GPS and GLONASS. The disadvantage relative to the conventional approach is the reduced ambiguity fixing success rate.

碩士
國立臺灣海洋大學
通訊與導航工程學系
107
Precise Point Positioning (PPP) is a standalone positioning method that is able to provide centimeter-level accuracy without utilizing the difference technique that is needed in the relative positioning method. In this thesis, a new positioning method based on the Melbourne-Wubbena combinations to solve the wide-laning ambiguity value is proposed, which can detect cycle slip and reduce measurement noise in real time. In this thesis, we introduce the application of different observables combinations, such as wide lane, narrow lane and ionosphere-free, and explore the difference between the ambiguity of wide lane and general single frequency. We perform various dual-frequency and dual-system experiments. Additionally, a kinematic positioning based on the triple-difference method is also conducted to serve as the reference trajectory for the verification of the kinematic experiments. The experimental results show that, in comparison with the traditional least squares method, the proposed method has better positioning performance and can be used in both static and dynamic cases. Additionally, we also provide a constrained least-squares method to mitigate the effect of multipath. The time period affected by multipath is investigated by residual error. The results show that this method is effective against the error caused by multipath.