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1
Xi, Xiaojin. "Analytical representation for ephemeris with short time-span : application to the longitude of Titan." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEO015/document.
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Les éphémérides issues d'intégrations numériques qui peuvent être facilement téléchargées des sites de l'IMCCE ou du JPL, ont une très bonne précision pour les observations récentes. En même temps, un autre type d'éphémérides, celles analytiques comme TASS, décrivent en détail le système dynamique par une représentation en combinaison de fréquences propres. Notre but est d'associer ces deux types d'éphémérides pour l'utiliser dans les études de la rotation des satellites naturelles. Cela signifie qu'il faut reconstruire des éphémérides à long terme et de haute précision montrant les caractéristiques du système comme les fréquences propres à partir des intégrations numériques. La principale difficulté est d'éviter l'intervalle de temps limité des éphémérides numériques. Dans notre travail, nous partons de la représentation des éléments d'orbite de Titan sur 10 000 ans issues de TASS comme exemple et comme standard. Nous expérimentons comment obtenir les fréquences propres sur 1000 ans d'éphémérides de TASS, et comment obtenir la représentation analytique de la longitude moyenne de Titan sur cet intervalle limité. A cause de cette durée de 1000 ans, au lieu de l'analyse en fréquence, nous utilisons la méthode des moindres carrées, en particulier pour les termes à longue période. L'efficacité et l’exactitude de l'ensemble de la méthode sont vérifiées en comparant les représentations de la longitude moyenne de Titan issue de TASS par la méthode des moindres carrées et par la représentation standard de TASS sur 10 000 ans. Finalement et c'est ce qui importe, nous obtenons une représentation du mouvement de Titan pour les 1000 ans d'éphémérides du JPL. Il existe une différence de 60 km dans l'amplitude du terme principal entre les représentations du JPL et de TASS. Cette différence est considérée comme issue du système. L'intervalle de temps limité des éphémérides influence les fréquences propres et induit des erreurs dans les termes à longues périodes comme contenant la longitude du nœud de Titan. Pour toutes les autres composantes ou presque, leurs amplitudes et phases sont similaires à celles de TASS. L'erreur de représentation est inférieure à 100 km sur 1000 ans et la déviation standard est de 26 km environThe numerical integration ephemeris, which are convenient to download from online service of IMCCE, or Horizons of JPL have very good precision based on recent observations. Meanwhile, another kind, the analytical ephemeris like TASS, describes in detail the dynamical system by combination representation of proper frequencies. We plan to make a connection between those two different type ephemeris, that it ’s benefited us to study the rotation of natural satellites with its high precision ephemeris, those instantaneous positions, velocity, and those system characteristics like proper frequencies. The main difficulty is to avoid the shortcoming of the limited interval of observation ephemeris.In our work, we take the combination representation of Titan with 10,000 years TASS ephemeris as an example and standard. Then, we experiment to obtain both the analytical representation of the mean longitude of Titan and the proper frequencies involved in it with 1,000 years TASS ephemeris by analysis frequency. Due to limited timespan, we extend the method with a least square method, especially for the long period terms. We verify the effectiveness and exactness of the whole method in rebuilt the combination representation.Finally and most important, we get the combination representation of Titan with 1000 years JPL ephemeris. Between the solution of JPL and the representation of TASS, there exists a 60 km difference in the amplitude of the major component, that is considered as a system difference. The limited interval ephemeris makes the influence of the proper frequency, which brings the error into the long period term like the one from the node of Titan. For nearly all other components, those amplitudes and phases are similar with the relative terms of TASS. The error of our representation is less than 100 kilometres over 1,000 years and the standard deviation is about 26 kilometres
2
Browne, Nathan J. James J. Light. "GPS ephemeris message broadcast simulation /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FBrowne.pdf.
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Thesis (M.S. in Systems Technology (Joint Command, Control, and Communications (C3))--Naval Postgraduate School, September 2005.Thesis Advisor(s): Dan C. Boger. Includes bibliographical references (p. 65-67). Also available online.
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Light, James J. "GPS ephemeris message broadcast simulation." Thesis, Monterey California. Naval Postgraduate School, 2005. http://hdl.handle.net/10945/2023.
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The warfighter constantly needs increased accuracy from GPS and a means to increasing this accuracy to the decimeter level is a broadcast ephemeris message containing GPS satellite orbit and clock corrections. The ephemeris message is produced at the GPS MCS (Master Control Station) which receives GPS signal data from NGA and Air Force worldwide and uses sophisticated software to produce the orbit and clock corrections. The problem is getting the ephemeris message to the tactical user in a forward operating area. This thesis proposed a notional architecture for pushing the ephemeris message to the tactical user. It then modeled the architecture and simulated the broadcast of the ephemeris message to a tactical user using NETWARS. The baseline architecture was simulated and analyzed and then additional constraints were placed upon the network to simulate a real-world model. The simulation results demonstrated that the architecture was feasible for ephemeris message broadcast with the constraints on time intervals between broadcasts, residual traffic and message size.
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Stacey, P. "Long-term ephemeris generation for mobile devices." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1389940/.
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GPS receivers in challenging signal reception areas can find it difficult to maintain continuous signal lock for the up-to 30 seconds needed to obtain the broadcast ephemeris from the satellites. It can take many minutes for receivers to obtain the ephemeris parameters from enough satellites to obtain a position fix. As well as users expecting a rapid time-to-first-fix (TTFF) when performing a warm start, the advent of the E-911 legislature in the USA also provides motivation for rapid TTFF with accurate positions. In this thesis, a scalable orbit prediction algorithm is developed to calculate an extended ephemeris of GPS satellites of up to 7 days on a mobile device to within an accuracy of 20 m rms (radial). The algorithm numerically integrates force models from a set of initial conditions, position and velocity, determined solely from the broadcast ephemeris. Forces used include Earth gravity models of varying resolution, third-body gravity effects, solar radiation pressure, relativity, and solid Earth tides. Adding these forces improves the ephemeris accuracy at the cost of the execution time, so research is undertaken to produce ephemeris data quickly whilst maintaining similar accuracy. An orbit determination algorithm is developed that uses a least-squares technique to optimise the computed orbit over multiple sets of previously observed broadcast ephemeris data. This modifies the estimate of the initial conditions made available to the orbit predictor, which then provides a modified ephemeris which has a substantially lower root-mean-square error. The algorithm again uses a suite of force models, and only broadcast ephemeris orbit data was utilised, no other satellite ephemeris is required. Studies determining the effect of modifying the a priori weights and the number of sets of ephemeris data used for observations are undertaken and results demonstrated on a HTC TyTN II mobile device. The orbit determination technique presented in this thesis is novel, in that it utilises only broadcast ephemeris parameters previously acquired by a single GPS receiver to modify the initial position and velocity for the orbit prediction algorithm. Previous techniques used either empirical modelling or least squares techniques to modify empirical parameters of the orbit prediction algorithm.
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Silva, Gelbart Souza. "Ephemeris belli Troiani Dictys Cretensis : estudo e tradução /." São José do Rio Preto, 2019. http://hdl.handle.net/11449/182250.
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Orientador: Cláudio AquatiBanca: Márcio Natalino Thamos
Banca: Norma Wimmer
Resumo: Neste trabalho, estudamos e traduzimos integralmente uma obra da literatura latina tardia conhecida como Ephemeris belli Troiani Dictys Cretensis (Diário da Guerra de Troia ), anônima e datável do século IV d. C. Ephemeris relata os eventos da Guerra de Troia do ponto de vista de um narrador em primeira pessoa que se apresenta como um soldado cretense de nome Díctis, alistado na tropa do comandante grego Idomeneu. A narração do prélio entre gregos e troianos, conhecida em literatura primordialmente pela leitura da Ilíada, de Homero, reveste se em Ephemeris de uma intenção racionalista ao diminuir os heróis à condição humana regular, ao diminuir a atuação dos deuses e ao estruturar a narrativa de forma lógica e cronológica. Composta de seis capítulos, precedidos por uma epístola e um prólogo, a obra é uma versão para o latim de um texto do século II originalmente em grego, o qual se encontra hoje fragmen tado. Ephemeris ganha importância no tocante à conservação do mito troiano, pois no Ocidente latino, desde o século I a. C. C., a história da Guerra de Troia era cada vez menos conhecida por intermédio dos poemas homérico e da literatura grega em geral em decorrência de uma precariedade na difusão do idioma grego por entre a elite romana. Acrescente se a esse fator a posterior e crescente pressão da Igreja que rechaçava os deuses não cristãos que habitavam a narrativa homérica. Desse modo, outras obras, compostas em latim, assumiram a transmissão da história troiana que nos...
Abstract: In this work, we study and translate integrally a late Latin work known as Ephemeris belli Troiani (Diary of the War of Troy ), anonymous and dating from the fourth century AD. Ephemeris reports the events of the Trojan War from the viewpoint of a first person narrator who presents himself as a Cretan soldier named Díctis, enlisted in the troop of the Greek com mander Idomeneu. The account of the battle between Greeks and Trojans, known in literature primarily by the reading of the Homer's Iliad, is dressed in Ephemeris of a rationalistic intention by diminishing the heroes to the regular human condition, by decr easing the performance of the gods and structuring the narrative logically and chronologically. Composed of six chapters, preceded by an epistle and a prologue, the work is a Latin version of a text of second century, written originally in Greek, which is now fragmented. Ephemeris gains importance with regard to the conservation of the Trojan myth. In the Latin West, since the first century BC, the story of Trojan War was less known through Homeric poems and Greek literature in general because of a precario usness in diffusion of the Greek language among the Roman elite. Add to this factor the later and growing pressure of the Church that rejected the polytheistic gods who inhabited the Homeric narrative. In this way other works composed in Latin assumed the transmission of the Trojan story that offered the Homeric epic. Of particular note is Ephemeris, which ...
Riassunto: In questo lavoro, studiamo e traduciamo integralmente uma opera latina conosciuta come Ephemeris belli Troiani (Diario della guerra di Troia ), anonima e risalente al secolo IV d. C. Ephemeris riporta gli eventi della guerra di Troia dal punto di vista di un narratore in prima persona che si presenta come un soldato chiamato Ditti Cretese, arruolato nell'esercito del comandante greco Idomeneo. La narrazion e del combattimento tra Greci e Troiani, nota in letteratura soprattutto per la lettura dela Iliade di Omero, si presenta in Ephemeris con un'intenzione razionalista poiché diminuire gli eroi alla condizione umana normale, ridurre il ruolo dele divinità e strutturare la narrazione in modo logico e cronologico. Composto da sei capitoli, preceduti da una lettera e un prologo, il libro è una versione latina di un testo greco del secolo II, che ora si conosce in frammenti. Ephemeris guadagni importanza per quan to riguarda la conservazione del mito troiano, perché nell'Occidente latino, dal primo secolo, la storia della guerra di Troia era sempre meno conosciuto attraverso i poemi omerici e l a letteratura greca in generale, a causa della bassa diffusione della li ngua greca tra l'elite romana. D'alt ra parte, l'ulteriore e crescente pressione della Chiesa respingeva le divinità non cristiane che abitavano la narrazione omerica. In questo modo, altre opere, composte in latino, presero la trasmissione della storia di Troia offerta dall'epopea omerica. Si distingue tra queste ...
Mestre
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Wolf, Robert. "Satellite orbit and ephemeris determination using inter satellite links." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=961611820.
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Thackrey, Keith R. "A geometric approach to determination of satellite ephemeris over a limited area." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43058.
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Range and,interferometric observations have been
examined for their potential, application in a geometric
approach to determination of satellite ephemeri. The
approach differs from the normal (dynamic) approach in that
each satellite position is treated as an independent state
variable or benchmark.
Programs have been developed that simulate and format
the input, data for the least squares estimation routines,
and perform statistical analyses of those results. Random error, tropospheric refraction errors, and atomic clock errors have been considered, and the range observation adjustment program directed to solve for clock errors.Master of Science
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Siqueira, Loram. "Contribution of Unesp on broadcast ephemeris and PDOP monitoring for GNSS in the IGMA - Trial Project /." Presidente Prudente, 2020. http://hdl.handle.net/11449/192427.
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Orientador: João Francisco Galera MonicoResumo: A modernização do GNSS (Global Navigation Satellite System) com a inclusão de novas constelações e melhorias nos sistemas já disponíveis foi avaliada com grande interesse na última década. A combinação de diferentes constelações de satélite expande as aplicações possíveis; portanto, o termo multi-GNSS apareceu para designar o uso desses múltiplos sistemas. O IGS (International GNSS Service), observando a necessidade dos usuários que começaram a usar o multi-GNSS, lançou em 2011 a proposta de projeto experimental IGMA (International GNSS Monitoring Assessment). O projeto visa criar um sistema internacional de análise GNSS com resultados que apresentem confiabilidade para usuários em todo o mundo. Na chamada para a participação como centro de análise a FCT-Unesp foi aceita como parte do projeto para avaliar dois dos quatro parâmetros propostos: Diluição da Precisão da Posição (PDOP) e a acurácia das efemérides transmitidas. Dos sistemas disponíveis, quatro foram escolhidos: GPS, Galileo. GLONASS e BeiDou nessa pesquisa. Foi realizado um estudo sobre o estado da arte para as aplicações de PDOP e WPDOP (Diluição da precisão ponderada na posição). Nas análises de acurácia, foi utilizado a correção entre o centro de fase e o centro de massa do satélite para comparar corretamente as efemérides finais e as transmitidas durante 600 dias (os 120 primeiros dias de cada ano entre 2015 e 2019). O GPS apresentou um RMSE 3D de 1,94 m, Galileo 1,19 m, GLONASS 7,21 m e BeiDou 3,19 m. As análi... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The modernization of GNSS (Global Navigation Satellite System) with the inclusion of new constellations and improvements in the already available systems has been assessed with great interest over the last decade. The combination of different satellite constellations expands the possible applications, so the term multi-GNSS appeared to designate the use of these multiple navigation systems. The IGS (International GNSS Service), observing the need of the users who started using multi-GNSS, launched in 2011 the proposal for the IGMA (International GNSS Monitoring Assessment) trial Project. It aims to create an international GNSS analysis system with results that present reliability for users around the world. In the call for participation as a center of analysis, FCT-Unesp was accepted as part of the trial project to evaluate the following parameters: Position Dilution of Precision (PDOP) and the accuracy of the broadcast ephemeris. Of the available systems, four were chosen: GPS, Galileo, GLONASS e BeiDou. A state-of-the-art study of PDOP and WPDOP (Weighted Position Dilution of Precision) applications was performed. On the accuracy analysis, it was used the phase center vector to correctly compare the final and broadcast ephemeris for 600 days (the first 120 days for each year between 2015 and 2019). The results show that GPS had an overall RMSE of 1.94 m, Galileo 1.94 m, GLONASS 7.21 m and BeiDou 3.19 m. The PDOP and WPDOP analyzes were carried out to evaluate the correlatio... (Complete abstract click electronic access below)
Mestre
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Lozada, Vidal C. "Space-based telescopes for the actionable refinement of ephemeris systems and test engineering." Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/10642.
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This thesis presents the results and activities related to the design, analysis, construction, test, and integration of a flight-qualified satellite, the Space-based Telescopes for the Actionable Refinement of Ephemeris (STARE) satellite. This project has been a collaboration, led by Lawrence Livermore National Laboratory (LLNL) and including the Naval Postgraduate School (NPS) and Texas AandM University. Of particular importance are the processes, experiences, and results of testing the payload and integrated STARE satellite. In addition, an analysis of testing requirements specifically appropriate for CubeSats, has been performed based on experience with larger satellites, and, finally, a thermal model has been developed for on-orbit thermal performance evaluation. The STARE satellite is currently scheduled to be a secondary payload mounted in the NPS CubeSat Launcher (NPSCuL), attached to the Atlas V Aft Bulkhead Carrier (ABC) on the Centaur upper stage. The goal of the STARE project is to improve Space Situational Awareness and, once the concept is validated, to develop a constellation that would be able to deliver highly refined optical data to improve current conjunction analysis.
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Gómez, Peinado Elísabet. "La Ephemeris Belli Troiani: edición del texto y estudio de los aspectos filológicos y literarios." Doctoral thesis, Universidad de Alicante, 2015. http://hdl.handle.net/10045/54016.
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En el siglo IV d.C. la Ephemeris belli Troiani de Lucio Septimio se presentaba, en su epistula y prologus introductorios, como una traducción latina de un original griego escrito por Dictis Cretense, que relató a modo de diario los sucesos de la guerra de Troya. Por otra parte, existían testimonios de eruditos bizantinos que hacían referencia también a este Dictis como autor de la Ephemeris belli Troiani. Sin embargo, no se tenía testimonio alguno de dicha obra griega, por lo que su existencia planteaba ciertas dudas. No fue hasta 1907 cuando, tras la publicación de un fragmento de papiro de la obra griega, se pudo constatar la existencia de dicho original griego, que vino a confirmarse más aún, si cabe, con otros tres fragmentos de papiro publicados con posterioridad. A partir de los fragmentos de papiro conservados (POxy. 4943, PTebt. 268, POxy. 2539, y POxy. 4944) podemos afirmar, en primer lugar, que la traducción latina de Lucio Septimio es libre o parafrástica, al menos en los cinco primeros libros de la obra griega, pues los restantes libros del original fueron resumidos en uno, según él mismo relata. En segundo lugar, la datación del fragmento más antiguo conservado se encuentra en torno al siglo II d.C. Por tanto, la composición del original griego estaría en torno a finales del siglo I o principios del siglo II y la gran popularidad que alcanzó dicha obra confirma su tradición abierta. La Ephemeris Belli Troiani se encuentra inmersa en el ambiente caracterizado por la Segunda Sofística, como se puede constatar en la información ofrecida por el prologus, el tratamiento de los discursos presentados en las embajadas por los caudillos griegos, etc. La novela, junto con la obra de Dares Frigio, comparten algunas características y recursos con otras novelas de temáticas variadas, como la utilización de la figura del testigo ocular, el recurso del manuscrito reencontrado, el hallazgo de la obra en una tumba, etc. que confieren mayor veracidad al relato y lo convierten en un relato “pseudohistórico”. La presentación de los sucesos de la guerra como hechos verídicos convierte la obra de Dictis en fuente literaria de la guerra de Troya, como alternativa veraz al relato homérico, para algunos eruditos bizantinos, como Malalas, cronista del siglo VI d.C. De esta manera encontramos en los bizantinos Malalas y Cedreno y en la obra anónima bizantina Eklogé episodios de los sucesos de la guerra de Troya que muestran un conocimiento de primera mano del relato de la Ephemeris Belli Troiani de Dictis. La Ephemeris Belli Troiani de Dictis Cretense y De excidio Troiae historia de Dares Frigio tuvieron trascendencia en la literatura posterior, es más, el relato que ambas obras presentaban sobre la guerra de Troya ha sobrevivido, aunque con adaptaciones, hasta nuestros días.
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Fredin, Elias. "GNSS undersökning : För bättre precision i smartphones." Thesis, Mittuniversitetet, Institutionen för informationssystem och –teknologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-36584.
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To be able to receive a position from a smartphone user is very valuable. Wit- hout this many applications would not work at all. For many applications the existing position libraries are not good enough, for example augmented reality applications which requires millimeter precision for a good experience. The goal of this report is to study if GNSS positioning can be improved for smartphones.The study focuses mostly on Android and has the goal of using the method “trilateration” to combine multiple satellites position and their distance to a receiver in order to calculate a real position. The projekt consists of two parts: and Android application and a Java Tomcat server. The android applica- tion uses the programming library “Location” to access raw GNSS-data for cal- culating the distance between the receiver and the satellites, which is called “pseudorange”, and the server functions as a REST API which provides GALI- LEO satellites current position. The project tries to combine these parameters in the Application to create a position. Although the report did not succeed in com- bining these parameters to calculate a position, it does describe of it is still pos- sible; which applications has succeeded before and what others ought to think about when starting similar studies. This project would require a bit more time to reach its end goal, but the fact that raw GNSS-data has become available to all developers on Android is a promising development since others may conti- nue or do their own research. This project focuses solely on GALILEO satelli- tes, mostly to time constraints. In future works all available satellite constella- tions should be used for better results.Att få en position av en smartphoneanvändare är mycket användbart, utan detta skulle många applikationer inte fungera alls. För många applikationer är den givna positionerings biblioteken inte tillräckligt bra dock, som t.ex. för augmen- ted reality applikationer som kräver millimeter-säker precision för en bra an- vändarupplevelse. Målet med denna rapport är att undersöka om GNSS-positio- nering kan förbättras inom smartphones. Undersökningen fokuserar mest på Android och har som målsättning att använda metoden “trilateration” för att kombinera satelliternas position och dess distans till en mottagare för att sedan räkna ut en verklig position. Projektet består av två delar: en Android applika- tion och en Java TomCat server. Android applikationen använder programme- rings biblioteket “Location” för att få tag på rå GNSS-data för att räkna ut di- stansen mellan satelliter och mottagaren, vilket kallas för “pseudorange”, och servern fungerar som ett REST API som returnerar GALILEO-satelliters nuva- rande position. Applikationen försöker kombinera pseudorange och satelliter- nas position med trilateration för at få ut mottagarens position. Rapporten lyck- as inte uppnå detta mål dock, men den beskriver hur det ändå är möjligt, vilka andra applikationer som lyckats och vad andra bör tänka på om de vill göra lik- nande studier. Det skulle behövas lite mer tid för att avsluta detta projekt, men faktumet att råa GNSS-data har blivit tillgänglig för alla Android-utvecklare, från att ha varit helt gömd, är en lovande utveckling då det låter andra forska på egen hand. Detta projekt fokuserar enbart på GALILEO satelliter, mestadels för tidsbegränsningar.
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Li, Shanna. "Une nouvelle réduction des anciennes observations de Phoebe et amélioration de son orbite." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEO008/document.
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Dans cette thèse, la recherche se concentre sur le re-calibrage des observations historiques de Phoebe, le 9ème satellite de Saturne, et l'amélioration de son orbite sur la base des données re-calibrés. La précision de calcul de l'orbite dépend de la qualité du modèle théorique (erreur interne) et de la précision des observations utilisées pour ajuster le modèle (erreur externe). Phoebe est loin de sa planète et des satellites majeurs. Le modèle théorique n'est pas très compliqué et l'erreur interne est bien connu et généralement bonne. Toutefois, l'erreur externe est en général inconnue et est la principale cause de l'erreur globale. Comme la luminosité de Phoebe est faible (Vmag = 16,5), il n'y a pas beaucoup d'observations faites dans le temps passé. La précision de son orbite n'est pas aussi bonne que celles des autres grands satellites de Saturne. Un modèle plus adéquat du mouvement du satellite devrait être construit non seulement sur la base des observations de haute-précision, mais aussi sur des données couvrant une période aussi longue que possible. Les observations de Phoebe sur plus de cent ans ont été calibré avec différents catalogues. Il y a quelques incohérences dans les données d'observation obtenues à partir de différents auteurs à différentes époques. De nombreuses observations ont été publiées dans différents formats; elles ne peuvent pas être utilisées directement pour ajuster le modèle dynamique; elles doivent être converties dans un format de données unifié et être corrigées pour des erreurs systématiques, avec les dernières constantes astronomiques dans le système de référence. Les premières observations de Phoebe ont une mauvaise précision et ne collent pas bien aux modèles. A cette époque, les catalogues utilisés ne contenaient pas assez d'étoiles avec une précision suffisante, donc il n'y avait pas beaucoup de étoiles du catalogue sur la plaque. En raison de la précision insatisfaisante des catalogues à l'époque, les positions des étoiles de référence ne sont pas très précises. Cela influe sur la position de Phoebe. Dans le présent travail, nous introduisons une méthode permettant, même si nous ne disposons pas des vraies plaques, de réduire les positions des satellites naturels avec des catalogues astrométriques modernes, tels que UCAC ou GAIA dans le futur. Après la re-calibration des données d'observation historiques, la réduction des observations a été effectuée et la nouvelle éphéméride de Phoebe on a été dérivée. La représentation synthétique au mouvement orbital de Phoebe à partir des éphémérides a été réaliséeIn this thesis, the research focuses on the recalibration of historical observations of Phoebe, the 9th satellite of Saturn, and its orbit improvement based on the re-calibrated data. The accuracy of orbit predictions depends on the theoretical model's quality (internal error) and on the quantity and accuracy of the observations used to fit the model (external error). Phoebe is far away from its planet and other major satellites, so that the theoretical model is not very complicated and the internal error is well known and generally good. However, the external error is generally unknown and is the main cause of the global error. Since the brightness of Phoebe is faint (Vmag=16.5), not so many observations have been made in the past time. The accuracy of its ephemeris is not as good as those of other major satellites of Saturn. A most adequate model of satellite motion should be built not only based on high-accurate recent observations but also on data over a period of time as long as possible. The observations of Phoebe over one hundred years have been calibrated with different catalogs. There are some inconsistencies in observational data obtained from different authors at different epochs. Many observations have been published in different formats; they cannot be used directly to fit the dynamical model, should be re-input into unified data format, and be corrected for systematic differences, with the latest astronomical constants and reference frame. The earliest observations of Phoebe have bad accuracy and not fit the models very well. At that time, the catalogues they used did not contain enough stars with a precise accuracy, so there were not many catalogue stars on the plate. Because of the unsatisfactory precision of the old catalogues at the epoch, the positions of the reference stars were not very precise. This brings today inaccuracy on the position of Phoebe. In the present work, we introduce a method, even if we do not have real plates, to reduce the positions of the natural satellites with modern astrometric catalogues, such as UCAC or GAIA in the future. After the re-calibration of historical observation data, reduction of observations has been completed and the new ephemeris Phoebe was derived. Then the synthetic representation of Phoebe's orbital motion from the ephemeris was provided
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Yin, Hang. "AN ADAPTIVE MULTI-FREQUENCY GPS TRACKING ALGORITHM, GPS CNAV MESSAGE DECODING, AND PERFORMANCE ANAYSIS." Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1407774289.
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Mastoridis, Klimis. "Casting the Greek newspaper : a study of the morphology of the ephemeris from its origins until the introduction of mechanical setting." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361424.
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Fazan, Antônio Juliano [UNESP]. "Predição de sombras de edifícios sobre vias urbanas com base em um modelo digital de elevações e dados de imagens aéreas de alta-resolução." Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/86818.
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fazan_aj_me_prud.pdf: 2364125 bytes, checksum: cd65fb05ed616ab1330e59a785328669 (MD5)Este trabalho apresenta uma metodologia para a predição de sombras projetadas por edifícios em vias urbanas usando imagens aéreas de alta-resolução e modelos digitais de elevações (MDE). Elementos de sombra podem ser usados na modelagem de informação contextual para, por exemplo, a extração semi-automática ou automática da malha viária a partir de imagens aéreas ou de satélite, principalmente em áreas urbanas densas. O contexto modela as relações entre os objetos numa imagem, como por exemplo, as relações entre edifícios e vias adjacentes. O uso de conhecimento contextual tem se tornado cada vez mais comum em processos de análise de imagem, principalmente em se tratando de cenas complexas. Este trabalho foi inspirado nas atuais possibilidades de se obter modelos digitais de elevações densos e acurados de áreas urbanas complexas a partir de dados de sistemas aerotransportados de varredura a laser. A metodologia proposta consiste de três etapas seqüenciais. Primeiramente, os contornos de telhados de edifícios são extraídos manualmente a partir de uma imagem altimétrica obtida pela transformação do MDE/laser. De maneira similar, os contornos dos limites das vias são extraídos, agora a partir da imagem de intensidade de retorno do pulso laser. Na etapa seguinte, os polígonos dos contornos de telhado são projetados nas vias adjacentes através do uso da projeção paralela. A direção das retas de projeção paralela é calculada a partir de dados de efemérides solares e do instante de tomada da imagem aérea. Finalmente, as partes dos polígonos de sombra que estão livres de obstruções perspectivas de edifícios são determinadas a partir da separação das regiões afetadas pela perspectiva de tomada.
This research presents a methodology for prediction of building shadows cast on urban roads using high-resolution aerial images and Digital Elevation Models (DEM). Shadow elements can be used in the modeling of contextual information, as e. g., in the semiautomatic or automatic road network extraction from satellite or aerial images, mainly in dense urban areas. Context models the relations among objects in an image, as e. g., the relations among buildings and adjacent roads. The use of contextual knowledge has become more common in image analysis processes, mainly if complex scenes are present. This research drew inspiration from the present possibilities of obtaining accurate and dense DEM from airborne laser scanning data of complex urban areas. The proposed methodology consists in three sequential steps. First, the building roof contours are manually extracted from an intensity image generated from the laser DEM. In similar way, the road side contours are extracted, now from the radiometric information of the laser scanning data. Second, the roof contour polygons are projected onto the adjacent roads by using the parallel projection. The direction of the parallel straight lines is computed from the solar ephemeris, which depends on the taken time of the aerial photograph. Finally, the parts of shadow polygons that are freed of building perspective obstructions are determined, given rise to new shadow polygons.
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Fazan, Antonio Juliano. "Predição de sombras de edifícios sobre vias urbanas com base em um modelo digital de elevações e dados de imagens aéreas de alta-resolução /." Presidente Prudente : [s.n.], 2007. http://hdl.handle.net/11449/86818.
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Orientador: Aluir Porfírio Dal PozBanca: Antônio Maria Garcia Tommaselli
Banca: Francisco Henrique de Oliveira
Resumo: Este trabalho apresenta uma metodologia para a predição de sombras projetadas por edifícios em vias urbanas usando imagens aéreas de alta-resolução e modelos digitais de elevações (MDE). Elementos de sombra podem ser usados na modelagem de informação contextual para, por exemplo, a extração semi-automática ou automática da malha viária a partir de imagens aéreas ou de satélite, principalmente em áreas urbanas densas. O contexto modela as relações entre os objetos numa imagem, como por exemplo, as relações entre edifícios e vias adjacentes. O uso de conhecimento contextual tem se tornado cada vez mais comum em processos de análise de imagem, principalmente em se tratando de cenas complexas. Este trabalho foi inspirado nas atuais possibilidades de se obter modelos digitais de elevações densos e acurados de áreas urbanas complexas a partir de dados de sistemas aerotransportados de varredura a laser. A metodologia proposta consiste de três etapas seqüenciais. Primeiramente, os contornos de telhados de edifícios são extraídos manualmente a partir de uma imagem altimétrica obtida pela transformação do MDE/laser. De maneira similar, os contornos dos limites das vias são extraídos, agora a partir da imagem de intensidade de retorno do pulso laser. Na etapa seguinte, os polígonos dos contornos de telhado são projetados nas vias adjacentes através do uso da projeção paralela. A direção das retas de projeção paralela é calculada a partir de dados de efemérides solares e do instante de tomada da imagem aérea. Finalmente, as partes dos polígonos de sombra que estão livres de obstruções perspectivas de edifícios são determinadas a partir da separação das regiões afetadas pela perspectiva de tomada.
Abstract: This research presents a methodology for prediction of building shadows cast on urban roads using high-resolution aerial images and Digital Elevation Models (DEM). Shadow elements can be used in the modeling of contextual information, as e. g., in the semiautomatic or automatic road network extraction from satellite or aerial images, mainly in dense urban areas. Context models the relations among objects in an image, as e. g., the relations among buildings and adjacent roads. The use of contextual knowledge has become more common in image analysis processes, mainly if complex scenes are present. This research drew inspiration from the present possibilities of obtaining accurate and dense DEM from airborne laser scanning data of complex urban areas. The proposed methodology consists in three sequential steps. First, the building roof contours are manually extracted from an intensity image generated from the laser DEM. In similar way, the road side contours are extracted, now from the radiometric information of the laser scanning data. Second, the roof contour polygons are projected onto the adjacent roads by using the parallel projection. The direction of the parallel straight lines is computed from the solar ephemeris, which depends on the taken time of the aerial photograph. Finally, the parts of shadow polygons that are freed of building perspective obstructions are determined, given rise to new shadow polygons.
Mestre
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Arora, Nitin. "High performance algorithms to improve the runtime computation of spacecraft trajectories." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49076.
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Challenging science requirements and complex space missions are driving the need for fast and robust space trajectory design and simulation tools. The main aim of this thesis is to develop new and improved high performance algorithms and solution techniques for commonly encountered problems in astrodynamics. Five major problems are considered and their state-of-the art algorithms are systematically improved. Theoretical and methodological improvements are combined with modern computational techniques, resulting in increased algorithm robustness and faster runtime performance. The five selected problems are 1) Multiple revolution Lambert problem, 2) High-fidelity geopotential (gravity field) computation, 3) Ephemeris computation, 4) Fast and accurate sensitivity computation, and 5) High-fidelity multiple spacecraft simulation. The work being presented enjoys applications in a variety of fields like preliminary mission design, high-fidelity trajectory simulation, orbit estimation and numerical optimization. Other fields like space and environmental science to chemical and electrical engineering also stand to benefit.
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Larocca, Ana Paula Camargo. "Análise de estratégias para processamento de redes geodésicas com o sistema de posicionamento global - GPS." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/18/18137/tde-24052006-101143/.
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O presente trabalho consiste de apresentação de metodologia para estudo, elaboração e análise de estratégias para processamento de observáveis GPS, para a constituição de redes geodésicas. No desenvolvimento deste trabalho foram utilizados os dados observados da rede geodésica do Estado de São Paulo, concluída em 1994. Esta rede é constituída por vinte e quatro pontos distribuídos pelo estado, mais o vértice CHUA, que é o vértice fundamental da triangulação do Sistema Geodésico Brasileiro. Através das estratégias elaboradas são analisados diversos fatores de importância relevante nos processamentos dos dados GPS, como: influência de dados meteorológicos no processamento de linhas bases longas; resultados de processamentos com efemérides transmitidas e precisas; resultados de processamentos com linhas bases de comprimentos homogêneos e menores ou igual a 150 km; resultados de processamentos considerando apenas duas horas e trinta minutos do tempo total de duração das sessões de observação. Os resultados dos ajustamentos destas estratégias são comparados entre si e se apresenta, então, análises e conclusões sobre a influência dos fatores analisadosThe present work consists in the presentation of a methodology for study, elaboration and analyses of strategies to process GPS observables for geodetic networks. In the development of this work, GPS data of the geodetic network of the State of Sao Paulo, concluded in 1994, were used. This network is composed twenty-four points scattered in the State, plus the vertex CHUA, that is the fundamental point of the triangulation of the brazilian geodesy system. Through the strategies elaborated, several factors of main importance for data GPS processing, are analyzed, such as: the influence of meteorological data processing of long baselines; the results of data processing with broadcast and precise ephemeris; the results of data processing with baselines of homogeneous lengths and smaller than or equal to 150 km; the results of data processing considering only two hours and thirty minutes of the total time of duration of the observation sessions. The results of the adjustment of these strategies are compared to each other, followed by analyses and conclusions about the influence of these factors on data processing
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Bourgoin, Adrien. "Contraintes sur les violations à la symétrie de Lorentz par analyse des données de télémétrie laser Lune." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066481/document.
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La relativité générale (RG) et le modèle standard des particules permettent de comprendre les quatre interactions fondamentales de la nature. La formulation d'une théorie quantique de la gravitation permettrait d'unifier ces deux tenants de la physique moderne. D'après les grandes théories d'unification, une telle union est possible moyennant la brisure de certaines symétries fondamentales apparaissant à la fois en RG et dans le modèle standard telle la symétrie de Lorentz. Les violations de la symétrie de Lorentz peuvent être paramétrées dans tous les domaines de la Physique par une théorie effective du champ appelée extension du modèle standard (SME). Une violation au principe d'invariance locale de Lorentz dans le secteur gravitationnel serait supposée engendrer des perturbations dans la dynamique orbitale des corps présents dans le système solaire, notamment la Lune. Ainsi, à partir des données extrêmement précises de télémétrie laser, l'orbite lunaire peut être minutieusement analysée afin de débusquer d'éventuelles anomalies dans son mouvement. Dans cette optique, ELPN (Ephéméride Lunaire Parisienne Numérique), une nouvelle éphéméride lunaire intégrée dans le cadre du formalisme SME a été développée durant la thèse. ELPN fournit les solutions au problème lunaire sous la forme de séries temporelles datées en temps dynamique barycentrique (TDB). Parmi les solutions numériquement intégrées, mentionnons la position et la vitesse du vecteur barycentrique Terre-Lune, les angles de librations lunaires, la différence entre le temps terrestre et le TDB, ainsi que l'ensemble des dérivées partielles intégrées depuis l'équation aux variations. Les prédictions de l'éphéméride ont été utilisées afin de réduire les observations lunar laser ranging (LLR). Dans le cadre de la RG, la dispersion des résidus s'est avérée en accord avec les dispersions calculées à partir des éphémérides INPOP13b et DE430. Dans le cadre du SME minimal, l'analyse des données LLR a permis de contraindre toutes violations à l'invariance locale de Lorentz. Une grande attention a été portée à l'analyse des incertitudes afin de fournir des contraintes réalistes. Ainsi, dans un premier temps, les combinaisons linéaires de coefficients SME ont été isolées puis ajustées aux observations. Puis, dans un second temps, les incertitudes réalistes ont été déterminées par une méthode de ré-échantillonnage. L'analyse des données de télémétrie laser Lune n'a pas permis de révéler de violations au principe d'invariance locale de Lorentz agissant au niveau de l'orbite lunaire. Les prédictions de la RG ont donc été validées avec des précisions absolues allant de 10-9 à 10-12General Relativity (GR) and the standard model of particle physics provide a comprehensive description of the four interactions of nature. A quantum gravity theory is expected to merge these two pillars of modern physics. From unification theories, such a combination would lead to a breaking of fundamental symmetry appearing in both GR and the standard model of particle physics as the Lorentz symmetry. Lorentz symmetry violations in all fields of physics can be parametrized by an effective field theory framework called the standard-model extension (SME). Local Lorentz Invariance violations in the gravitational sector should impact the orbital motion of bodies inside the solar system, such as the Moon. Thus, the accurate lunar laser ranging (LLR) data can be analyzed in order to study precisely the lunar motion to look for irregularities. For this purpose, ELPN (Ephéméride Lunaire Parisienne Numérique), a new lunar ephemeris has been integrated in the SME framework. This new numerical solution of the lunar motion provides time series dated in temps dynamique barycentrique (TDB). Among that series, we mention the barycentric position and velocity of the Earth-Moon vector, the lunar libration angles, the time scale difference between the terrestrial time and TDB and partial derivatives integrated from variational equations. ELPN predictions have been used to analyzed LLR observations. In the GR framework, the residuals standard deviations has turned out to be the same order of magnitude compare to those of INPOP13b and DE430 ephemerides. In the framework of the minimal SME, LLR data analysis provided constraints on local Lorentz invariance violations. Spetial attention was paid to analyze uncertainties to provide the most realistic constraints. Therefore, in a first place, linear combinations of SME coefficients have been derived and fitted to LLR observations. In a second time, realistic uncertainties have been determined with a resampling method. LLR data analysis did not reveal local Lorentz invariance violations arising on the lunar orbit. Therefore, GR predictions are recovered with absolute precisions of the order of 10-9 to 10-12
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Ruiz, Rodilla Alvaro. "Vers une "poétique de l'inventaire" de José Emilio Pacheco : poésie et journalisme (1973-1983)." Thesis, Toulouse 2, 2016. http://www.theses.fr/2016TOU20056.
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Inventario (1973-2014) est une chronique de presse de longue haleine, basée sur l’empathie avec le lecteur et sur des formes de démocratisation de la culture, publiée dans le supplément Diorama de la cultura puis dans la revue Proceso de Mexico, et à laquelle le poète José Emilio Pacheco (1939-2014) se consacra jusqu’aux derniers instants de sa vie. La poésie trouve dans ces pages un espace privilégié de publication, de critique et de récits des faits. Notre travail de compilation de 1973 à 1983 embrasse l’époque de consolidation d’Inventario ainsi que le développement d’une écriture où se côtoient poésie et journalisme, histoire et littérature. Le poème de circonstance, abondant dans Inventario parmi d’autres formes expressives, permet une lecture nouvelle et intermédiale de l’oeuvre de l’auteur mexicain ; cette forme poétique loin de se trouver empesée par les événements promeut une pédagogie du passé. De manière complémentaire, Inventario se profle lui-même comme une poétique : en tant que possibilité d’habiter le monde en empathie avec les auteurs, les lecteurs et les textes ; en tant que manière de désacraliser et de démonter les hiérarchies latentes de la littérature ; en tant que versifcation de l’Histoire dans des fragments qui sont à la recherche de l’Autre et qui posent le problème d’un imaginaire multilingue, “expropriateur” de ressources naturelles provenant d’autres langues ; unechronique toujours éphémère et changeanteInventario is a long-lasting press chronicle - based on a feeling of empathy with the reader and on many forms of cultural democratization - which was published in the Mexican newspaper supplement Diorama de la cultura, then in Proceso magazine. The poet José Emilio Pacheco (1939-2014) devoted himself to this creation up to the last minutes of his life. Poetry finds in these pages a privileged publication space in which criticism and factual narratives are also involved. Our compilation - from 1973 to 1983 - embraces Inventario's consolidation period and the development of a rich writing in which poetry and journalism stand along with history and literature. Circumstance poems, which are very present in Inventario together with other expressive forms, engage an innovative and intermedial reading of the Mexican poet's legacy. Such poetical form is rarely starched by recent events, but promotes on the contrary an educational method to better apprehend the past. In a complementary manner, Inventario presents itself as a poetics for what it embodies: a possibility of inhabiting the world by following the readers’/ writers’ empathy; a form of desacralization and destruction of inherent and concealed literature hierarchies; a fragmented versification of History which seeks for otherness and questions a multi-linguistic imaginary system - an imaginary “expropriator” of other languages’ natural resources; an ephemeral and ever-changing chronicle
Inventario (1973-2014) es una crónica empática, democratizante y de largo aliento, publicada en el suplemento Diorama de la cultura y luego en la revista Proceso de México y a la que el poeta José Emilio Pacheco (1939-2014) dedicó hasta los últimos minutos de su vida. La poesía halla, en estas páginas un espacio privilegiado de publicación, de crítica y de relación de los hechos. Nuestro trabajo de recopilación de 1973 a 1983 abarca la época de consolidación de Inventario así como el desarrollo de una escritura donde colindan poesía y periodismo, historia y literatura, hasta alcanzar formas devaluadas e incluso inusitadas. Nunca entorpecido por los acontecimientos sino sobrellevado como una pedagogía del pasado, el poema de circunstancia, abundante en Inventario, permite, entre otras formas expresivas, una lectura nueva e intermedial de la obra del autor mexicano. De manera complementaria, el Inventario se perfla como una posible poética: posibilidad de habitar el mundo en comunión con autores, lectores y textos, forma de desacralizar y desmoronar las jerarquías latentes en la literatura, versifcación de la Historia en fragmentos que buscan al Otro y plantean un imaginario multilingüe, « expropiador » de recursos naturales de otras lenguas, siempre efímero y cambiante
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Yi-HwaChang and 張玴華. "The Study on Extending GPS Broadcast Ephemeris." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/47147977273497765677.
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碩士國立成功大學
航空太空工程學系碩博士班
100
Global Positioning System (GPS) has become more popular today. With the increase of personal mobile products, more demands from navigation and positioning systems are issued. Among them, the higher accuracy in position and velocity are one of the important key factors. A traditional GPS receiver usually takes 12.5 minutes to download the navigation message to provide location-based services, so that shortening the time-to-first-fix (TTFF) to achieve fast-positioning is a common goal of many research tasks. Since the precise ephemeris can be downloaded from International GNSS Service (IGS), it is possible to use the ephemeris to strengthen TTFF performance. The primary approach of this study is to use Extended Kalman Filter (EKF) that converts the above IGS precise orbit (as measurement) into the precise broadcast ephemeris (as estimated state). Since the measurement partial differential is a complex mathematics model, therefore, adding the state error, the measurement error, and etc. with EKF approach can improves the accuracy of the state and the derived model. In this study, the satellite’s positions at the sequential epochs have been predicted by the EKF-estimated precise broadcast ephemeris and compared with the true precise orbit. The average error of the satellite position can be reduced from 3 meters to 0.4 meters. When decreasing the number of measurements, combining with the satellite’s velocity is useful to enhance the accuracy of satellite position. In this study, the accuracy comparison between EKF and Batch Least Squares Filter (BLSF) has been analyzed. Under the same condition, the accuracy obtained with using EKF and BLSF are 0.4 meters and 0.62 meters, respectively. Clearly, the result shows that the orbit accuracy using EKF approach is better than that using BLSF.
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Tzu-HsiangWei and 魏子翔. "Hourly and Weekly GPS Broadcast Ephemeris Prediction." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/72674105702250098954.
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CHING-YICHANG and 張清義. "Using GPS Velocity to Enhance Broadcast Ephemeris." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/13284575713829758338.
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Lin, Jia-He, and 林家和. "Algorithm Design for GPS Satellite Long-Term Ephemeris." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/78358484718320233379.
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碩士國立臺灣海洋大學
通訊與導航工程系
97
When the GPS receiver is opened, its the first speed of the positioning is depended on the receiver which has the available GPS navigation message. If the GPS receiver doesn’t have any GPS navigation message, we will call it to be the cold start. The warm start has the available almanac. And if it has the ephemeris, it will be called the hot start. At present the specification of the cold start and the warm start, their positioning time is less than 35 seconds. And the hot starting specification has been possible to achieve which in one second then locates. In order to achieve the high sensitivity and the fast positioning, we will make the GPS receiver to maintain under the similar hot starting condition. The present paper mainly uses a satellite ephemeris to estimate the latter three day of satellite position and to achieve the GPS Satellite Long-Term Ephemeris. We will use the satellite orbital mechanics and movement theory to create the equation of two-body motion, and add the correction term of the perturbation (non-uniform spherical earth and n-body ) to correct the disturbance of the satellite which caused by external force. We will do the numerical integration to obtain the satellite position, so that GPS receiver will keep the hot start and achieve the purpose of the rapid positioning. Keyword：1.Two-body motion; 2. Non-uniform spherical earth; 3. N-body motion; 4. Numerical integration.
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Chen, Chien-Ming, and 陳見明. "Application of Averaging Method in Satellite's Ephemeris Extension Problem." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/42351981125314892716.
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碩士國立臺灣海洋大學
通訊與導航工程學系
100
The prediction of satellite orbit has played a crucial role in Global Navigation Satellite System (GNSS). For a GNSS receiver, ephemeris extension will enable fast positioning even in a cold-start situation. In this thesis, we propose an average method to estimate the Kepler elements, which in turn can be used to calculate the satellite position. An analytical solution is obtained by the method of averaging, where the satellite orbit perturbation considered in the thesis, includes nun-uniform spherical earth effect, n-body motion disturbances. In compared with the traditional numerical method (such as Runge-Kutta method), the principal advantages of the analytical solutions lies in that prediction of orbit error does not accumulate over time; and in the mean time the computation efficiency also improves.
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Liu, Kang-Tai, and 劉康台. "Satellite Orbit Perturbation Problem Analysis and Long-Term Ephemeris Application." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/35570716836656267135.
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碩士國立臺灣海洋大學
通訊與導航工程學系
99
The of satellite orbit prediction has played a crucial role in GNSS navigation. Before the user's position can be actually determined, the receiver needs to download the navigation message in order to predict the satellite's position. This is a very time-consuming process and the receiver needs to download the message once every one to two hours. In this paper, we construct a perturbation- based method to calculate and predict satellite's orbit. The method is main based an numerical integration of perturbed satellite orbital equation, By considering the nun-uniform spherical earth effect, n-body, solar radiation pressure and earth tide, we can predict in an accurate manner the position of the satellite for a 3-day period, and we only need one single epoch of navigation data.
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Wolf, Robert [Verfasser]. "Satellite orbit and ephemeris determination using inter satellite links / by Robert Wolf." 2001. http://d-nb.info/961611820/34.
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Chen, Jia-Hung, and 陳家宏. "The Estimation of GPS Broadcast Ephemeris with Using The Least-Squares Method." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/79559012574558458889.
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碩士國立成功大學
航空太空工程學系碩博士班
97
The traditional GPS receiver must download broadcast ephemeris from the satellites. Downloading the information for guidance will cost 30 seconds, which will cost approximate 12.5 minutes for download the entire guidance message. The AGPS method setups the GPS receiver through the AGPS server, that will download the broadcast ephemeris from the satellites beforehand. The AGPS server will pass the broadcast ephemeris on to the user receiver by the internet connection, which will reduces the time to first fix ( TTFF ), and achieves the fast navigation. The primary method of this research is to use the precise ephemeris International GNSS Service, which provides and decides the observation Partial differential model to convert into a more useful broadcast ephemeris by using the Least-Squares method. The observation Partial differential model is a complex mathematics model. Therefore, the condition error, the observation error, and etc. will be added to prove the accuracy of the derived model. Computing respectively of the satellite position is compared with using precise ephemeris and broadcast ephemeris that is able to decrease the maximum error from 14 meter to 0.8 meter. In addition, it has the same navigation result by using broadcast ephemeris, but the users can download this ephemeris several hours before they go outdoors. It could increase the convenience for the users as well.
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Liu, Tien-Lei, and 劉添雷. "GPS Satellite Orbit and Ephemeris Prediction using Neural Network and Polynomial Curve Fitting." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/29834849833867772763.
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碩士國立臺灣科技大學
機械工程系
96
The Global Positioning System（GPS）is a set of real-time positioning system. So long as the signal surrounding the user's receiver and satellite is not obstructed, the GPS could provide the positioning three-dimension service for any users on earth in the absence of influences of weather, time, place etc. However, in addition to the accuracy of location, velocity, and time, the length of time the GPS receiver needs to fix for the first use under different circumstances is also an important performance parameter that cannot be ignored. Whether the GPS satellite is equipped with ephemeris is also closely related to the time the GPS receiver needs for the first fix. In this experiment, we attempts to construct a fundamental period orbit model, clock correction model, satellite orbit period, fundamental error of estimated orbit and so on to predict GPS satellite orbit in future 7 days and clock correction by several tools such as neural network and polynomial curve fitting and operating in coordination with the GPS’s satellite orbit's in related cyclical characteristics and the known GPS satellite ephemeris. In the experiment, the average error of the orbit estimation may be less than 500 meters on the 5th day and the average error of the clock correction estimation may be less than 15 nanoseconds in the 7 days. Even if, in the Generalization tests of this experimental technique by other dates, the average error of the orbit estimation may be less than 500 meters at the 3rd day and the corresponded average error of the clock correction estimation may be less than 62 nanoseconds.
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Liou, Yih-Bor, and 劉佾博. "Near Real-Time Kinematic Satellite Ephemeris Determination for the ROCSAT-3 Satellites:Using MicroLab-1 Data." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/44150816437687249183.
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碩士國立成功大學
測量工程學系
87
ROCSAT-3 is a constellation of eight meteorological satellites which is a cooperative project between Taiwan and the U.S. The altitude of ROCSAT-3 satellites is about 800 kilometers and the satellites will be launched in 2003. ROCSAT-3 satellites receive GPS occulted signals that traverse the earth''s atmosphere, and then derives the refractive index of the atmosphere through which GPS signals have passed during occultation events. With the refractive index, one can retrieve the moisture, temperature and pressure of atmosphere. In addition, by analyzing near real-time globally distributed occultations simultaneously, global real-time weather forecast can be implemented. To retrieve meteorological parameters from occultation observation, one must know the orbits of both GPS satellites and ROCSAT-3 satellites. GPS satellites'' orbit can be obtained from GPS broadcast ephemeris, IGS predicted ephemeris or IGS precise ephemeris. The purpose of this study is to determined the ROCSAT-3 orbit in near real-time. Since ROCSAT-3 satellites will not be launched till 2003, so the data of MicroLab-1, which is the preliminary experiment of the ROCSAT-3 project, is used in this paper. To estimate the orbit position using 24 IGS tracking station distributed uniformly on the earth, we consider MicroLab-1 as a rapid moving station, and apply the ionosphere-free carrier phase third-differential method in this study. Besides, the tropospheric correction model, solid earth tide correction and antenna phase center correction of the tracking stations, mass center correction of satellite and earth rotation correction are incorporated. Since the phase third-differential method will produce accumulative error, the ionosphere-free pseudorange dual-differential method is introduced to reduce the error. The results indicate that the corrected ionosphere-free carrier phase third-differential method and GPS broadcast ephemeris combine achieve to the accuracy of 1.028、1.098 and 1.613 meter on the three-axis components in the earth-fixed coordination system; whereas with IGS''s GPS predicted ephemeris, the method can achieve the accuracy of 0.942、0.857 and 1.141 meter.
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Harris, Robert B. Ph D. "Incorporation of the Global Positioning System modernization signals into existing smoother-based ephemeris generation processes." 2008. http://hdl.handle.net/2152/18103.
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The introduction of M-Code to the GPS signal structure can redefine the accuracy of the broadcast ephemeris. Existing ephemeris generation systems use dual frequency observations, obtained through the tracking of existing precise codes on the L1 and L2 frequencies. These codes are modulated using Binary Phase Shift Key (BPSK) modulation. The modernization signal M-Code is modulated using Binary Offset Carrier (BOC) modulation. In this study pseudorange observables derived from the tracking of M-Code are proven to have greater accuracy than those from existing precise codes, given equivalent receiver designs and operating conditions. In addition, the error due to specular multipath is derived. These general models of noise and multipath can be applied to any BOC modulated signals, including Galileo and QZSS. When applied to M-Code, the models predict that the maximum multipath error in the pseudorange is reduced in magnitude by 50% compared to the existing precise codes. However the range of multipath delays for which M-Code observables exhibit multipath is approximately twice that associated with existing precise BPSK codes. Existing ephemeris generation processes use the ionosphere free combination and carrier phase smoothing of the pseudorange to form smoothed pseudoranges. The smoothed pseudoranges are then input as measurements to an ephemeris filter. The analytic models of multipath error in the pseudorange and carrier phase observables are applied to predict errors in the smoothed pseudorange. Multipath error, amplified by ionosphere free combination, causes a bias in the smoothed pseudorange when parameterized as a function of multipath delay. There are conditions under which the bias is zero mean, and in those conditions multipath is suppressed. The mechanism for those conditions is solved and discussed, for both BOC and BPSK signal tracking. The solution of carrier phase multipath for BOC modulated signals also admits solutions with a special quality not seen in the BPSK solution. There are multipath delays for which the carrier phase multipath is identically zero regardless of the multipath phase. The zero carrier phase multipath condition may be the most promising feature associated with observables derived from BOC modulated codes.text
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Shu-Shien, Lin, and 林書賢. "Improving the Accuracy of Orbit Ephemeris of the ROCSAT-1 & -2 Satellites Using the IGS Network." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/92487350555314404461.
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碩士國立成功大學
測量工程學系
88
ABSTRACT The ROCSAT-1 satellite was successfully launched on January 27, 1999. The satellite is orbiting the Earth at an altitude of 630 kilometers with an inclination of 35 degrees. The ROCSAT-1 satellite is mainly designed to carry out ocean color imaging and scientific research missions. The launch date of ROCSAT-2 satellite is scheduled at the middle of 2003, and the satellite will orbit the Earth at an altitude of 891 kilometers with an inclination of 99 degrees. The ROCSAT-2 satellite is mainly designed to perform near real-time high resolution remote sensing of the ocean and landmass in the vicinity of Taiwan. The accuracy demand of the ROCSAT-2 satellite is higher than the ROCSAT-1 satellite for that the external orientation parameters are needed for ROCSAT-2 missions. There are no original GPS observation data downlinked from the ROCSAT-1, ROCSAT-2 satellites for postprocessing applications. As a result, the goal of this study is to calculate the systemic errors of pseudorange observations, including GPS satellite clock error, GPS broadcast ephemeris error and ionospheric delay, by using IGS tracking stations distributed uniformly around the world. The above systemic errors are turned into a correction to orbital position. Test results indicate that with a good geometry distribution of tracking stations and known PRN values of observed GPS satellites when SA effect is on, the accuracy of the navigation position can be improved from 60 meters to 10 meters, and when SA effect is off, PRN values of observed GPS staellite are not important to the results, and the accuracy of the navigation position can be improved from 20 meters to 10 meters.
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Nai-Hui, Liao, and 廖乃慧. "The updated orbital ephemeris of high mass X-ray binary Cyg X-3 detected from monitoring X-ray telescopes." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/4eunye.
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碩士國立中央大學
天文研究所
106
Cyg X-3 is a high-mass X-ray binary system composed by a Wolf-Rayet star and a compact object. Its 4.8 hr orbital modulation profile is caused by the strong stellar wind from companion with a specific form. We analyzed the light curve collected by the all sky monitor (ASM) on broad Rossi X-ray Timing Explorer (RXTE), the Monitor of All-sky X-ray Image (MAXI) and The Burst Alert Telescope (BAT) on broad Swift. To make clear orbital modulation profiles, the light curve from each observation was divided into several segments and folded by a linear ephemeris, then cross-correlated with a standard template. Combined with previous results, we discovered the significant third order orbital period derivative and obtained the orbital period derivatives of P ̇=(1.29±0.18)〖"×" 10〗^(-9) 〖yr yr〗^(-1)、P ̈=(-6.13±1.41)〖"×" 10〗^(-11) 〖yr〗^(-1)、P ⃛=(2.31±0.96)〖"×" 10〗^(-12) 〖 yr〗^(-2) using O-C method. These high order orbital period derivatives are likely due to the variation of mass outflow. We also considered that the orbital derivatives are caused by that Cyg X-3 is in a hieratical triple system but found that this model can hardly fit into our observation result.
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Hsu, Chien-An, and 許建安. "A Study of the Point Positioning Influence by Chebyshev Polynomial Fitting on Broadcast Ephemeris -A Case Study of Taichung Monitoring Network." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/4j59q8.
Full textAbstract:
碩士國立中興大學
土木工程學系所
98
In GPS satellite positioning, the satellite coordinates require to be continuously updated to obtain coordinates of ground single-point positioning by using determined coordinates and method of backward intersection. Real-time satellite coordinates are determined by broadcast ephemeris. The broadcast ephemeris forecasts the data every two hours. If the data are used to calculate satellite coordinates, the data would be enormous and calculation is complex. Therefore, this study applied Chebyshev polynomials fitting method to reduce computation process and save data memory space. This study analyzed satellite data from the TC02 GPS base station in Taichung City, applied Chebyshev polynomials to fit broadcast ephemeris, and discusses impacts of sampling time and fitting order on 3D components and precision results of satellite coordinates for ground point-positioning after fitting. In selection of fitting order, this study applied the 12th order Chebyshev polynomials to fit experimental fitting order, because too many orders may require longer sampling time and cannot be used in calculation of real-time satellite positioning. Thus, the 12th order was selected to balance sampling time and fitting precision. The fitting results showed that the fitting precision of 3D coordinate components is lower than ±2m when using satellite coordinates of Chebyshev polynomials fitting. The satellite coordinates after fitting were used to calculate single-point positioning results of TC02 GPS base station. Errors of the coordinate components were less than ±6m. The precision of fitting results were 0.2~0.5m higher than that of satellite coordinates obtained from original equation. These findings can be used to reduce the computation procedure of satellite coordinates needed for GPS satellite single-point positioning. This study can improve the shortcomings in the equations of computing satellite coordinates using broadcast ephemeris to lift the speed of single-point positioning.