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Journal articles on the topic 'Geoid determination'

Author: Grafiati
Published: 4 June 2021
Last updated: 10 February 2022

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1

Marques, Éder Teixeira, William Rodrigo Dal Poz, and Gabriel Do Nascimento Guimarães. "GEOID MODELLING USING INTEGRATION AND FFT ASSOCIATED WITH DIFFERENT GRAVIMETRIC REDUCTION METHODS." Revista Brasileira de Geofísica 36, no. 1 (March 20, 2018): 81. http://dx.doi.org/10.22564/rbgf.v36i1.909.

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ABSTRACT. A vertical reference system is characterized by a vertical datum and a set of scientific altitudes. In the case of orthometric altitudes, the geoid is used as a reference surface, equipotential surface of the gravity field of the Earth that better fits, in the sense of the Least Square Method, to the mean sea level. This study aimed to determine the geoid by applying two processes for calculation of residual ondulation, the integration and the Fast Fourier Transform. These techniques were applied to the values of the residual anomalies obtained from different methods of gravimetric reduction, the Helmert’s Second Method of Condensation, Bouguer and Rudzki. Two test areas were used. For area 1, the best gravimetric geoid was obtained by applying 1D planar FFT with the Helmert’s SecondMethod of Condensation. For area 2, the best gravimetric geoid was obtained through the application of integration and the Rudzki’s reduction. It can be concluded that the physical characteristics of both areas are relevant in the determination of the geoid and that additional procedures must be applied to improve the geoid determination, mainly, in area 2 whose physical characteristics are more heterogeneous than in area 1.Keywords: Geoid, GeoFis 1.0, Gravimetric Reduction, FFT, Stokes Integral. RESUMO. Um sistema vertical de referência é caracterizado por um datum vertical e pelo conjunto de altitudes científicas. No caso das altitudes científicas adotadas serem as ortométricas utiliza-se como superfície de referência o geoide, superfície equipotencial do campo da gravidade da Terra que melhor se ajusta, no sentido do método dos mínimos quadrados, ao nível médio do mar. O objetivo desse trabalho foi determinar o geoide aplicando dois processos de cálculo da ondulação residual, a integração e a Transformada Rápida de Fourier. Essas técnicas foram empregadas aos valores de anomalias residuais obtidas a partir de diferentes métodos de redução gravimétrica, Segundo Método de Condensação de Helmert, Bouguer e Rudzki. Foram utilizadas duas áreas de teste. Verificou-se que para a área 1 o melhor geoide gravimétrico foi obtido pela aplicação da FFT planar 1D juntamente com o Segundo Método de Condensação de Helmert. Para a área 2 o melhor geoide gravimétrico foi obtido pela aplicação da integração e da redução de Rudzki. Conclui-se que as características físicas das duas áreas são relevantes na determinação do geoide e que procedimentos complementares devem ser aplicados para melhorar a determinação do geoide, principalmente, na área 2 cujas características físicas são mais heterogêneas do que da área 1. Palavras-chave: Geoide, GeoFis 1.0, Redução gravimétrica, FFT, Integral de Stokes.
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2

Forsberg, R., A. Olesen, L. Bastos, A. Gidskehaug, U. Meyer, and L. Timmen. "Airborne geoid determination." Earth, Planets and Space 52, no. 10 (October 2000): 863–66. http://dx.doi.org/10.1186/bf03352296.

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3

Manandhar, Niraj, and Shanker K.C. "Geoid Determination and Gravity Works in Nepal." Journal on Geoinformatics, Nepal 17, no. 1 (June 4, 2018): 7–15. http://dx.doi.org/10.3126/njg.v17i1.23003.

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Gravimetric geoid plays the important role in the process of local/regional geoidal undulation determination. This approach uses the residual gravity anomalies determined by the surface gravity measurement using the gravimeter together with best fit geopotential model, with the geoid undulations over the oceans determined from the method of satellite altimetry. Mass distribution, position and elevation are prominent factors affecting the surface gravity. These information in combination with geopotential model helps in satellite orbit determination, oil, mineral and gas exploration supporting in the national economy. The preliminary geoid thus computed using airborne gravity and other surface gravity observation and the accuracy of computed geoid was likely at the 10-20cm in the interior of Nepal but higher near the border due to lack of data in China and India. The geoid thus defined is significantly improved relative to EGM –08 geoid.
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4

Erol, Serdar, Emrah Özögel, Ramazan Alper Kuçak, and Bihter Erol. "Utilizing Airborne LiDAR and UAV Photogrammetry Techniques in Local Geoid Model Determination and Validation." ISPRS International Journal of Geo-Information 9, no. 9 (September 2, 2020): 528. http://dx.doi.org/10.3390/ijgi9090528.

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This investigation evaluates the performance of digital terrain models (DTMs) generated in different vertical datums by aerial LiDAR and unmanned aerial vehicle (UAV) photogrammetry techniques, for the determination and validation of local geoid models. Many engineering projects require the point heights referring to a physical surface, i.e., geoid, rather than an ellipsoid. When a high-accuracy local geoid model is available in the study area, the physical heights are practically obtained with the transformation of global navigation satellite system (GNSS) ellipsoidal heights of the points. Besides the commonly used geodetic methods, this study introduces a novel approach for the determination and validation of the local geoid surface models using photogrammetry. The numeric tests were carried out in the Bergama region, in the west of Turkey. Using direct georeferenced airborne LiDAR and indirect georeferenced UAV photogrammetry-derived point clouds, DTMs were generated in ellipsoidal and geoidal vertical datums, respectively. After this, the local geoid models were calculated as differences between the generated DTMs. Generated local geoid models in the grid and pointwise formats were tested and compared with the regional gravimetric geoid model (TG03) and a high-resolution global geoid model (EIGEN6C4), respectively. In conclusion, the applied approach provided sufficient performance for modeling and validating the geoid heights with centimeter-level accuracy.
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Jürgenson, Harli, Kristina Türk, and Jüri Randjärv. "DETERMINATION AND EVALUATION OF THE ESTONIAN FITTED GEOID MODEL EST-GEOID 2003 / ESTIJOS GEOIDO MODELIO EST-GEOID 2003 SUDARYMAS IR VERTINIMAS / СОЗДАНИЕ И ОЦЕНКА МОДЕЛИ ГЕОИДА ЭСТОНИИ EST-GEOID2003." Geodesy and Cartography 37, no. 1 (April 15, 2011): 15–21. http://dx.doi.org/10.3846/13921541.2011.558339.

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This paper focuses on issues related to the calculation of a high-precision fitted geoid model on Estonian territory. Model Est-Geoid2003 have been used in Estonia several years in geodesy and other applications. New data from precise levelling, new global models and terrestrial gravity data give plenty of possibilities for updates and accuracy evaluation. The model is based on a gravimetric geoid. From the gravimetric data gathered, a gravimetric geoid for Estonia was calculated as an approximately 3-km net using the FFT method. After including the new gravimetric data gathered, the gravimetric geoid no longer had any significant tilt relative to the height anomalies derived from GPS-levelling points. The standard deviation between the points was 2.7 cm. The surface of the calculated gravimetric geoid was fitted by high-precision GPS-levelling points. As a result, a height transformation model was determined to reflect the differences between the normal heights of BK77 and the ellipsoidal heights of EUREF-EST97 on Estonian territory. The model was originally called Est-Geoid2003 and is part of the official national geodetic system in Estonia. The model is updated and evaluated here using precise GPS-levelling points obtained from different measurement campaigns. In 2008–2010 the preliminary results from the latest precise levelling sessions became available, leading to a significant increase in the number of precise GPS-levelling points. Both networks are part of the Estonian integrated geodetic network. Using very precise levelling connections from new levelling lines, normal heights of several RGP points were calculated additionally. Misclosure of 300 km polygons are less than 2–3 mm normally. Ealier all precisely levelled RGP points were included into fitting points. Now many new points are available for fitting and independent evaluation. However, the use of several benchmarks for the same RGP point sometimes results in a 1–2 cm difference in normal height. This reveals problems with the stability of older wall benchmarks, which are widely used in Estonia. Even we recognized, that 0.5 cm fitted geoid model is not achievable using wall benchmarks. New evaluation of the model Est-Geoid2003 is introduced in the light of preliminary data from new precise levelling. Model accuracy is recognised about 1.2 cm as rms. Santrauka Akcentuojami klausimai, susiję su tiksliausio Estijos geoido modelio skaičiavimu. Šis modelis Estijoje geodezijoje ir kitose mokslo bei technikos šakose taikomas nuo 2003 metų. Nauji precizinės niveliacijos duomenys, nauji globalieji geopotencialo modeliai ir žemyno gravimetriniai duomenys – prielaidos geoido modeliui atnaujinti ir jo tikslumui įvertinti. Modelio pagrindas – gravimetrinis geoidas. Pagal surinktus gravimetrinius duomenis Estijos geoidas buvo apskaičiuotas greitųjų Furjė tranformacijų (FFT) metodu, sukuriant apie 3 km akių tinklą. Įtraukus naujuosius gravimetrinius duomenis, gravimetrinis geoidas daugiau nebeturi aukščių anomalijų. Vidutinė kvadratinė paklaida – 2,7 cm. Apskaičiuoto gravimetrinio geoido paviršius susietas su aukščių sistema pagal GPS niveliacijos taškus. 2008–2010 m. gavus precizinės niveliacijos duomenis, žymiai padidėjo GPS niveliacijos taškų skaičius bei jų tikslumas, nes precizinės niveliacijos poligonų iki 300 km nesąryšiai gauti mažesni nei 2–3 mm. Įvertinus naujo Estijos geoido modelio tikslumą nustatyta 1,2 cm vidutinė kvadratinė paklaida. Резюме Акцентируются вопросы, касающиеся вычисления точной модели геоида Эстонии. Эта модель применяется в Эстонии с 2003 г. в геодезии и других отраслях науки и техники. Новые данные высокоточной нивеляции, новые глобальные модели геопотенциала, а также гравиметрические данные создают предпосылки для обновления модели геоида и оценки его точности. Модель основана на гравиметрическом геоиде. Модель геоида Эстонии была вычислена быстрым методом Фурье с использованием всех гравиметрических данных и созданием сети 3×3 км. После использования новых гравиметрических данных в геоиде не оказалось значительного превышения высот по сравнению с точками, измеренными методом GPS. Среднеквадратическая погрешность составила 2,7 см. Вычисленная модель геоида была соединена с системой высот по точкам GPSнивелирования. Благодаря новым данным по высокоточной нивеляции, полученным в 2008–2010 гг., значительно увеличилось количество точек GPSнивелирования и тем самым увеличилась точность геоида, так как невязки полигонов нивелирования составляют всего 2–3 мм. Оценив точность нового геоида Эстонии, выявлено среднеквадратическое отклонение в 1,2 см.
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6

Lukoševičius, Viktoras. "DFHRS-BASED COMPUTATION OF QUASI-GEOID OF LATVIA." Geodesy and Cartography 39, no. 1 (April 12, 2013): 11–17. http://dx.doi.org/10.3846/20296991.2013.788827.

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In geodesy, civil engineering and related fields high accuracy coordinate determination is needed, for that reason GNSS technologies plays important role. Transformation from GNSS derived ellipsoidal heights to orthometric or normal heights requires a high accuracy geoid or quasi-geoid model, respectively the accuracy of the currently used Latvian gravimetric quasi-geoid model LV'98 is 6–8 cm. The objective of this work was to calculate an improved quasi-geoid (QGeoid) for Latvia. The computation was performed by applying the DFHRS software. This paper discusses obtained geoid height reference surface, its comparisons to other geoid models, fitting point statistics and quality control based on independent measurements.
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7

Truong, Nguyen Ngoc, and Tran Van Nhac. "Determination of the constant Wo for local geoid of Vietnam and it’s systematic deviation from the global geoid." Tạp chí Khoa học và Công nghệ biển 17, no. 4B (December 15, 2017): 138–44. http://dx.doi.org/10.15625/1859-3097/17/4b/13001.

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Constant Wo, defining the geoid, has important applications in the area of physical geodesy. With the development of artificial Earth satellite, constant Wo for the global geoid approximating the oceans on Earth can be calculated from an expansion of spherical harmonics - Stokes constants determined by observation of perturbations in artificial satellite’s orbits. However, the Stokes constants are limited, therefore the geoid constant Wo could not be calculated for local geoid (state geoid) from the mentioned expansion of spherical harmonics. In this paper, we present a method to determine the constant Wo for local geoid of Vietnam, using generalized Bruns formula and Neyman boundary problem. The initial data used are Faye gravity anomalies surveyed on land and sea of Southern Vietnam. The constant Wo is then used to calculate the systematic deviation of the local geoid of Vietnam from the global geoid EGM - 96.
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8

Sjöberg, Lars E. "The topographic bias in gravimetric geoid determination revisited." Journal of Geodetic Science 9, no. 1 (January 1, 2019): 59–64. http://dx.doi.org/10.1515/jogs-2019-0007.

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Abstract The topographic potential bias at geoid level is the error of the analytically continued geopotential from or above the Earth’s surface to the geoid. We show that the topographic potential can be expressed as the sum of two Bouguer shell components, where the density distribution of one is spherical symmetric and the other is harmonic at any point along the normal to a sphere through the computation point. As a harmonic potential does not affect the bias, the resulting topographic bias is that of the first component, i.e. the spherical symmetric Bouguer shell. This implies that the so-called terrain potential is not likely to contribute significantly to the bias. We present three examples of the geoid bias for different topographic density distributions.
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9

Ayhan, M. Emin. "Geoid determination in Turkey (TG-91)." Bulletin Géodésique 67, no. 1 (March 1993): 10–22. http://dx.doi.org/10.1007/bf00807293.

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10

Jiang, Z., and H. Duquenne. "On fast integration in geoid determination." Journal of Geodesy 71, no. 2 (January 21, 1997): 59–69. http://dx.doi.org/10.1007/s001900050075.

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11

Ghanem, Essam. "GPS-gravimetric geoid determination in Egypt." Geo-spatial Information Science 4, no. 1 (January 2001): 19–23. http://dx.doi.org/10.1007/bf02826631.

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12

Novák, P., M. Kern, K. P. Schwarz, M. G. Sideris, B. Heck, S. Ferguson, Y. Hammada, and M. Wei. "On geoid determination from airborne gravity." Journal of Geodesy 76, no. 9-10 (February 1, 2003): 510–22. http://dx.doi.org/10.1007/s00190-002-0284-3.

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13

Nov�k, P. "Geoid determination using one-step integration." Journal of Geodesy 77, no. 3-4 (June 1, 2003): 193–206. http://dx.doi.org/10.1007/s00190-003-0314-9.

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14

Sideris, Michael G. "Fourier geoid determination with irregular data." Journal of Geodesy 70, no. 1-2 (November 1995): 2–12. http://dx.doi.org/10.1007/bf00863415.

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15

Sjöberg, L. E., and M. Bagherbandi. "Quasigeoid-to-geoid determination by EGM08." Earth Science Informatics 5, no. 2 (May 3, 2012): 87–91. http://dx.doi.org/10.1007/s12145-012-0098-7.

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16

Sjöberg, L. "Comments to X. Li and Y. M. Wang (2011) Comparisons of geoid models over Alaska computed with different Stokes' kernel modifications, JGS 1(2): 136-142." Journal of Geodetic Science 2, no. 1 (January 1, 2012): 38–39. http://dx.doi.org/10.2478/v10156-011-0022-y.

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Comments to X. Li and Y. M. Wang (2011) Comparisons of geoid models over Alaska computed with different Stokes' kernel modifications, JGS 1(2): 136-142Li and Wang recently compared geoid determination by various gravimetric methods for modifying Stokes' formula vs. using GPS/levelling geoid heights as a reference model. Possible large systematic errors in the differences of gravimetric and GPS/levelling geoid models deteriorate the results and conclusions. Moreover, spectral combination, the only stochastic method in the study, was applied in an unrealistic way.
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17

Sjüberg, L. "Quality Estimates in Geoid Computation by EGM08." Journal of Geodetic Science 1, no. 4 (January 1, 2011): 361–66. http://dx.doi.org/10.2478/v10156-011-0014-y.

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Quality Estimates in Geoid Computation by EGM08The high-degree Earth Gravitational Model EGM08 allows for geoid determination with a resolution of the order of 5'. Using this model for estimating the quasigeoid height, we estimate the global root mean square (rms) commission error to 5 and 11 cm, based on the assumptions that terrestrial gravity contributes to the model with an rms standard error of 5 mGal and correlation length 0:01° and 0:1°, respectively. The omission error is estimated to—0:7Δg [mm], where Δg is the regional mean gravity anomaly in units of mGal.In case of geoid determination by EGM08, the topographic bias must also be considered. This is because the Earth's gravitational potential, in contrast to its spherical harmonic representation by EGM08, is not a harmonic function at the geoid inside the topography. If a correction is applied for the bias, the main uncertainty that remains is that from the uncertainty in the topographic density, which will still contribute to the overall geoid error.
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18

Kearsley, A. W. H., and R. M. Eckels. "The determination of the geoid-spheroid separation for GPS levelling and applications." Exploration Geophysics 20, no. 2 (1989): 185. http://dx.doi.org/10.1071/eg989185.

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The heights which are obtained from global positioning system (GPS) satellite observations are measured with respect to an earth-centred ellipsoid and are not, as a result, generally useful for surveying and engineering. In order to become useful they must be transformed into orthometric heights, that is, heights which are measured with respect to the actual level reference surface termed the geoid. The parameter which enables this transformation is N, the geoid height or geoid-ellipsoid separation.This paper reviews the capabilities of the GPS system for height measurements, describes the various methods used to evaluate N from gravimetry, and explores the suitability of these methods in the various applications in which height measurements from the GPS may be used.
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Reguzzoni, Mirko, Daniela Carrion, Carlo Iapige De Gaetani, Alberta Albertella, Lorenzo Rossi, Giovanna Sona, Khulan Batsukh, et al. "Open access to regional geoid models: the International Service for the Geoid." Earth System Science Data 13, no. 4 (April 21, 2021): 1653–66. http://dx.doi.org/10.5194/essd-13-1653-2021.

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Abstract. The International Service for the Geoid (ISG, https://www.isgeoid.polimi.it/, last access: 31 March 2021) provides free access to a dedicated and comprehensive repository of geoid models through its website. In the archive, both the latest releases of the most important and well-known geoid models, as well as less recent or less known ones, are freely available, giving to the users a wide range of possible applications to perform analyses on the evolution of the geoid computation research field. The ISG is an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). Its main tasks are collecting, analysing, and redistributing local, regional, and continental geoid models and providing technical support to people involved in geoid-related topics for both educational and research purposes. In the framework of its activities, the ISG performs research taking advantage of its archive and organizes seminars and specific training courses on geoid determination, supporting students and researchers in geodesy as well as distributing training material on the use of the most common algorithms for geoid estimation. This paper aims at describing the data and services, including the newly implemented DOI Service for geoid models (https://dataservices.gfz-potsdam.de/portal/?fq=subject:isg, last access: 31 March 2021), and showing the added value of the ISG archive of geoid models for the scientific community and technicians, like engineers and surveyors (https://www.isgeoid.polimi.it/Geoid/reg_list.html, last access: 31 March 2021).
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20

Jigena, Bismarck, Manuel Berrocoso, Cristina Torrecillas, Juan Vidal, Ignacio Barbero, and Alberto Fernandez-Ros. "Determination of an experimental geoid at Deception Island, South Shetland Islands, Antarctica." Antarctic Science 28, no. 4 (February 24, 2016): 277–92. http://dx.doi.org/10.1017/s0954102015000681.

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AbstractDeception Island is an active volcano located in Bransfield Strait. Its volcanic activity is linked to the presence of gravity anomalies that influence the definition of the geoid. In this paper, a precise undulation geoid model (GeoiDEC14) has been computed from GPS, gravimetric and levelling measurements. GeoiDEC14 highlights local anomalies of the island that match with hot spots, such as the minimum values shown in Fumarole Bay and Whalers Bay (fumarole areas), or the maximum values found in the remains of lava at Colatinas, Black Glacier and Murature Point. Comparison of GeoiDEC14 with global models always shows negative values due to an average of 18.80 m for our model compared to 19.80–20.60 m for models such as ITSG-Grace2014s, EGM08, AIUG-Grace03s or EGM96. This difference is due to the lack of resolution of global models and to the volcanic activity on the island. To confirm the results, the same measurements were taken on nearby Livingston Island. The values of geoid undulation on this island reaffirm the lack of detail in the global geoid in the area, presenting an average of 18.90 m, similar to the average value of GeoiDEC14.
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21

Sjöberg, L. E. "The geoid or quasigeoid – which reference surface should be preferred for a national height system?" Journal of Geodetic Science 3, no. 2 (September 1, 2013): 103–9. http://dx.doi.org/10.2478/jogs-2013-0013.

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Abstract Most European states use M. S. Molodensky’s concept of normal heights for their height systems with a quasigeoid model as the reference surface, while the rest of the world rely on orthometric heights with the geoid as the zero-level. Considering the advances in data caption and theory for geoid and quasigeoid determinations, the question is which system is the best choice for the future. It is reasonable to assume that the latter concept, in contrast to the former, will always suffer from some uncertainty in the topographic density distribution, while Molodensky’s approach to quasigeoid determination has a convergence problem. On the contrary, geoid and quasigeoid models computed by analytical continuation (e.g., rcr technique or KTH method) have no integration problem, and the quasigeoid can always be determined at least as accurate as the geoid. As the numerical instability of the analytical continuation is better controlled in the KTH method vs. the rcr method, we propose that any future height system be based on normal heights with a quasigeoid model computed similar to or directly based on the KTH method (Least squares modification of Stokes formula with additive corrections).
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Zhan-ji, Yang, and Chen Yong-qi. "DETERMINATION OF THE HONG KONG GRAVIMETRIC GEOID." Survey Review 36, no. 279 (January 2001): 23–34. http://dx.doi.org/10.1179/sre.2001.36.279.23.

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23

Völgyesi, L. "Local geoid determination based on gravity gradients." Acta Geodaetica et Geophysica Hungarica 36, no. 2 (June 2001): 153–62. http://dx.doi.org/10.1556/ageod.36.2001.2.3.

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24

Zhang, K. F., A. H. Dodson, and W. Chen. "Factors affecting FFT gravimetric geoid determination precision." Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy 25, no. 1 (January 2000): 31–37. http://dx.doi.org/10.1016/s1464-1895(00)00006-5.

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LI, Fei, Jian-Li YUE, and Li-Ming ZHANG. "Determination of Geoid by GPS/Gravity Data." Chinese Journal of Geophysics 48, no. 2 (March 2005): 326–30. http://dx.doi.org/10.1002/cjg2.657.

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26

Iliffe, J. C., W. J. Griffiths, and E. L. Message. "LOCALISED GEOID DETERMINATION FOR ENGINEERING CONTROL SURVEYS." Survey Review 35, no. 275 (January 2000): 320–28. http://dx.doi.org/10.1179/sre.2000.35.275.320.

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27

Lee, Jenn-Taur, and D. F. Mezera. "CONCERNS RELATED TO GPS-DERIVED GEOID DETERMINATION." Survey Review 35, no. 276 (April 2000): 379–97. http://dx.doi.org/10.1179/sre.2000.35.276.379.

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28

Serpas, J. G., and C. Jekeli. "Local geoid determination from airborne vector gravimetry." Journal of Geodesy 78, no. 10 (February 18, 2005): 577–87. http://dx.doi.org/10.1007/s00190-004-0416-z.

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29

Oluyori, Paul Dare, and Sylvester Okiemute Eteje. "IMPROVING THE LOCAL GEOMETRIC GEOID MODEL OF FCT ABUJA ACCURACY BY FITTING A HIGHER ORDER/DEGREE POLYNOMIAL SURFACE." FUDMA JOURNAL OF SCIENCES 4, no. 3 (September 11, 2020): 114–20. http://dx.doi.org/10.33003/fjs-2020-0403-276.

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The improvement of the accuracy of a local geometric geoid model using the same data set (geoid heights) requires the fitting of a higher degree polynomial surface to the data set. Consequently, this paper presents improving the local geometric geoid model of FCT, Abuja accuracy by fitting a higher order polynomial surface. A fifth degree polynomial surface was fit to the existing geoid heights of 24 points used previously for the determination of the geometric geoid model of the study area to improve its accuracy. The least squares adjustment technique was applied to compute the model parameters, as well as the fit. The RMSE index was applied to compute the accuracy of the model. The computed accuracy (0.081m) of the model was compared with those of the previously determined geoid models (Multiquadratic, 0.110m and Bicubic, 0.136m models) of the study area to determine which of the models best fit the study area, as well as has the highest resolution. The comparison result shows that the fifth degree polynomial surface best fit the study area.
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Marotta, Giuliano Sant’Anna, and Roberta Mary Vidotti. "DEVELOPMENT OF A LOCAL GEOID MODEL AT THE FEDERAL DISTRICT, BRAZIL, PATCH BY THE REMOVE-COMPUTE-RESTORE TECHNIQUE, FOLLOWING HELMERT'S CONDENSATION METHOD." Boletim de Ciências Geodésicas 23, no. 3 (September 2017): 520–38. http://dx.doi.org/10.1590/s1982-21702017000300035.

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Abstract: There are several techniques for determining geoid heights using ground gravity data, the geopotential models, the astro-geodetic components or a combination of them. Among the techniques used, the Remove-Compute-Restore (RCR) technique has been widely applied for the accurate determination of the geoid heights. This technique takes into account short, medium and long wavelength components derived from the elevation data obtained from Digital Terrain Models (DTM), ground gravity data and global geopotential models, respectively. This technique can be applied after adopting the procedures to compute gravity anomalies and, then, the geoid model, considering the integration of different wavelengths mentioned, and their compatibility with the vertical datum adopted. Thus, this paper presents the procedures, involving the RCR technique, following Helmert's condensation method, and its application to compute one local geoid model for the Federal District, Brazil. As a result, the local geoid model computed for the studied area was consistent with the available values of geoid heights derived from geometrical levelling technique supported by GNSS positioning.
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31

Hoa, Ha Minh. "ESTIMATING THE GEOPOTENTIAL VALUE W0 OF THE LOCAL GEOID BASED ON DATA FROM LOCAL AND GLOBAL NORMAL HEIGHTS OF GPS/LEVELING POINTS IN VIETNAM." Geodesy and Cartography 39, no. 3 (September 26, 2013): 99–105. http://dx.doi.org/10.3846/20296991.2013.823705.

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Currently, the determination of geopotential value W0 of local geoid that best fits local mean sea level at the Zero Tide Gauge Station is getting important in building the National Geoid-Based Vertical System. Ha Minh Hoa (2007) and Kotsakis et al. (2012) recommended a method, which estimates the geopotential value W0 of local geoid at the Zero Tide Gauge Station based on equations of relation between the local and global normal heights or between the local and global height anomalies at GPS/leveling points regularly located on the whole territory. The objective of this paper is to determine conditions for estimating the geopotential value W0 of local geoid at the Zero Tide Gauge Station accomplished for whole territory of Vietnam.
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32

Kim, Kwang Bae, Hong Sik Yun, and Ha Jung Choi. "Accuracy Evaluation of Geoid Heights in the National Control Points of South Korea Using High-Degree Geopotential Model." Applied Sciences 10, no. 4 (February 21, 2020): 1466. http://dx.doi.org/10.3390/app10041466.

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Precise geoid heights are not as important for understanding Earth’s gravity field, but they are important to geodesy itself, since the vertical datum is defined as geoid in a cm-level accuracy. Several high-degree geopotential models have been derived lately by using satellite tracking data such as those from Gravity Recovery and Climate Experiment (GRACE) and Gravity Field and Steady-State Ocean Circulation Explorer (GOCE), satellite altimeter data, and terrestrial and airborne gravity data. The Korean national geoid (KNGeoid) models of the National Geographic Information Institute (NGII) were developed using the latest global geopotential models (GGMs), which are combinations of gravity data from satellites and land gravity data. In this study, geoid heights calculated from the latest high-degree GGMs were used to evaluate the accuracy of the three GGMs (European Improved Gravity model of Earth by New techniques (EIGEN)-6C4, Earth Gravitational Model 2008 (EGM2008), and GOCE-EGM2008 combined model (GECO)) by comparing them with the geoid heights derived from the Global Navigation Satellite System (GNSS)/leveling of the 1182 unified control points (UCPs) that have been installed by NGII in South Korea since 2008. In addition, the geoid heights derived from the KNGeoid models were compared with the geoid heights derived from the GNSS/leveling of the 1182 UCPs to assess the accuracy of the KNGeoid models in terms of relative geoid heights for further gravimetric geoid determination studies in South Korea. As a result, the EGM2008 model could be selected as the suitable GGM from among the three GGMs for determining a gravimetric geoid model for South Korea.
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33

CHEN, Junyong, Jiangcheng LI, Jinsheng NING, and Dingbo CHAO. "Geoid Determination on China Sea and its Merge with the Geoid in China Mainland." Chinese Journal of Geophysics 46, no. 1 (January 2003): 29–36. http://dx.doi.org/10.1002/cjg2.313.

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34

Vega Fernádez, Alonso, Oscar Lücke Castro, and Jaime Garbanzo Leon. "Geoid heights in Costa Rica, Case of Study: Baseline Along the Central Pacific Zone." Revista Ingeniería 30, no. 1 (November 12, 2019): 1–20. http://dx.doi.org/10.15517/ri.v30i1.35839.

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A precise orthometric height (H) and orthometric height difference (ΔH) determination is required in many fields like construction, geodesy and geophysics. H is often obtained from an ellipsoidal height (h) and geoid height (N) of a geoid model (GM) because this computation does not have the spirit leveling restrictions on long distances. However, the H accuracy depends on the GM local area adaptation, and current global geoid models (GGMs) have not been yet evaluated for Costa Rica. Therefore, this paper aims to determine which GGM maintains a better fit with a GPS/levelling baseline that contains the gravity full spectrum. A 74 km baseline was measured using GPS, spirit leveling and gravity measurements to validate the N computed from EGM2008, EIGEN-6C4, GECO, EGM96, GGM05C and GOCO05C. First, an absolute N assessment was made, where geoid height from the GGMs (NGGM) were directly compared to the geometric geoid heights (Ngeo) obtained from GPS and spirit levelling. A bias fit (Nbias) of about 2 m was computed from this comparison for most GGMs with respect to the local vertical reference surface (W0). By subtracting the Nbias, a relative geoid height (ΔN) assessment was designed to compare the differences between GGM relative geoid height (ΔNGGM) and geometric relative geoid height (ΔNgeo) on segments along the baseline. The ΔN comparison shows that EGM2008, EIGEN-6C4 and GECO better represent the Costa Rican Central Pacific Coastal Zone and over long distances, ΔH can be computed with a decimeter to centimeter precision.
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35

Mishra, Upendra Nath, and Jayanta Kumar Ghosh. "DEVELOPMENT OF A GRAVIMETRIC GEOID MODEL AND A COMPARATIVE STUDY." Geodesy and cartography 42, no. 3 (September 22, 2016): 75–84. http://dx.doi.org/10.3846/20296991.2016.1226368.

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Site specific geoid model is prerequisite for accurate determination of orthometric heights. No geoid model has been developed so far for India or any of its part. So, development of a geoid model for India or its part is of utmost need to make use of GNSS data towards determination of orthometric heights. In this research work, an attempt has been made to develop geoid undulation models by gravimetric method using Molodensky’s concept. Component parameters in line with the Remove – Compute – Restore (RCR) technique have been used recursively. Models have been developed for two study areas: one of these lies in and around Dehradun (30° 19′ N, 75° 04′E) in Uttarakhand state, India in lower Himalayan region having highly undulating topography and the other near Hyderabad (17° 30′N, 78°30′E) in Telengana state of India having gentle topography. The model has been tested for 7 stations in the first study area and accuracy has been found to be 17.5 cm; whereas, for the second area accuracy has been found to be 7.0 cm for 24 test stations. Further, the performances of the developed models have been evaluated with those from three global geoid models namely EIGEN6C4, EIGEN6C3stat and EGM2008; and have been found to be similar or better in case of first study and for second study area far more superior. Thus, local/regional geoid undulation model requiring accuracy better than 20 cm for any study area may be developed adopting the method. However, the optimality in the number and density of gravity stations may be considered as a future scope of work.
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36

Tenzer, R., R. Čunderlík, N. Dayoub, and A. Abdalla. "Application of the BEM approach for a determination of the regional marine geoid model and the mean dynamic topography in the Southwest Pacific Ocean and Tasman Sea." Journal of Geodetic Science 2, no. 1 (January 1, 2012): 8–14. http://dx.doi.org/10.2478/v10156-011-0019-6.

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Application of the BEM approach for a determination of the regional marine geoid model and the mean dynamic topography in the Southwest Pacific Ocean and Tasman SeaWe apply a novel approach for the gravimetric marine geoid modelling which utilise the boundary element method (BEM). The direct BEM formulation for the Laplace equation is applied to obtain a numerical solution to the linearised fixed gravimetric boundary-value problem in points at the Earth's surface. The numerical scheme uses the collocation method with linear basis functions. It involves a discretisation of the Earth's surface which is considered as a fixed boundary. The surface gravity disturbances represent the oblique derivative boundary condition. The BEM approach is applied to determine the marine geoid model over the study area of the Southwest Pacific Ocean and Tasman Sea using DNSC08 marine gravity data. The comparison of the BEM-derived and EGM2008 geoid models reveals that the geoid height differences vary within -25 and 18 cm with the standard deviation of 6 cm. The DNSC08 sea surface topography data and the new marine geoid are then used for modelling of the mean dynamic topography (MDT) over the study area. The local vertical datum (LVD) offsets estimated at 15 tide-gauge stations in New Zealand are finally used for testing the coastal MDT. The average value of differences between the MDT and LVD offsets is 1 cm.
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37

Abdalla, A., H. Fashir, A. Ali, and D. Fairhead. "Validation of recent GOCE/GRACE geopotential models over Khartoum state - Sudan." Journal of Geodetic Science 2, no. 2 (January 1, 2012): 88–97. http://dx.doi.org/10.2478/v10156-011-0035-6.

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Validation of recent GOCE/GRACE geopotential models over Khartoum state - SudanThis paper evaluates a number of latest releases of GOCE/GRACE global geopotential models (GGMs) using the GPS-levelling geometric geoid heights, terrestrial gravity data and existing local gravimetric models. We investigate each global model at every 5 degree of spherical harmonics. Our analysis shows that the satellite-only models derived by space-wise and time-wise approaches (SPW_R1, SPW_R2 TIM_R1 and TIM_R2), GOCO01S together with EGM08 (combined model) are very distinct and consistent to the local data, which guarantees one of them to be selected as the best of candidate models and then to be utilized in our further geoid studies. One of Satellite-only models will be employed for acquiring the long wavelength geoid component which is one of major steps in the geoid determination. EGM08 will be used to compensate and restore the missing gravity data points in the un-surveyed parts within the target area. We expect further improvements in geoid studies in Sudan due to the improved medium wavelength part of the gravity field from GOCE mission.
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38

Moritz, H. "A contemporary perspective of geoid structure." Journal of Geodetic Science 1, no. 1 (March 1, 2011): 82–87. http://dx.doi.org/10.2478/v10156-010-0010-7.

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A contemporary perspective of geoid structureThe present paper reviews the contemporary state of definition and theory of the geoid. Key features are:quasigeoid, external gravitational field from satellites and its analytical downward continuation to the Earth's interior, data combination by least-squares collocation, and a new view of gravity reduction. This is done under the modern systematic perspective provided by the possibility of a purely geometric satellite determination of the Earth' surface by GPS combined with satellite altimetry.
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39

Janák, Juraj, Petr Vańiček, Ismael Foroughi, Robert Kingdon, Michael B. Sheng, and Marcelo C. Santos. "Computation of precise geoid model of Auvergne using current UNB Stokes-Helmert’s approach." Contributions to Geophysics and Geodesy 47, no. 3 (September 1, 2017): 201–29. http://dx.doi.org/10.1515/congeo-2017-0011.

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AbstractThe aim of this paper is to show a present state-of-the-art precise gravimetric geoid determination using the UNB Stokes-Helmert’s technique in a simple schematic way. A detailed description of a practical application of this technique in the Auvergne test area is also provided. In this paper, we discuss the most problematic parts of the solution: correct application of topographic and atmospheric effects including the lateral topographical density variations, downward continuation of gravity anomalies from the Earth surface to the geoid, and the optimal incorporation of the global gravity field into the final geoid model. The final model is tested on 75 GNSS/levelling points supplied with normal Molodenskij heights, which for this investigation are transformed to rigorous orthometric heights. The standard deviation of the computed geoid model is 3.3 cm without applying any artificial improvement which is the same as that of the most accurate quasigeoid.
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40

Holota, P. "Variational methods in geoid determination and function bases." Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy 24, no. 1 (January 1999): 3–14. http://dx.doi.org/10.1016/s1464-1895(98)00003-9.

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41

Lehmann, R. "Studies in altimetry-gravimetry problems for geoid determination." Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy 24, no. 1 (January 1999): 47–51. http://dx.doi.org/10.1016/s1464-1895(98)00009-x.

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42

Zhang, K. "On the determination of a new Australian geoid." Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy 24, no. 1 (January 1999): 61–66. http://dx.doi.org/10.1016/s1464-1895(98)00011-8.

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43

Kühtreiber, N. "Precise geoid determination using a density variation model." Physics and Chemistry of the Earth 23, no. 1 (January 1998): 59–63. http://dx.doi.org/10.1016/s0079-1946(97)00242-5.

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44

Schwarz, Klaus-Peter, and Ye Cai Li. "What can airborne gravimetry contribute to geoid determination?" Journal of Geophysical Research: Solid Earth 101, B8 (August 10, 1996): 17873–81. http://dx.doi.org/10.1029/96jb00819.

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45

Bae, Tae-Suk, Jisun Lee, Jay Hyoun Kwon, and Chang-Ki Hong. "Update of the precision geoid determination in Korea." Geophysical Prospecting 60, no. 3 (December 20, 2011): 555–71. http://dx.doi.org/10.1111/j.1365-2478.2011.01017.x.

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46

Hejrati, Soheil, and Mehdi Goli. "Terrain effect in geoid determination by geopotential models." Journal of Geospatial Information Technology 6, no. 2 (September 1, 2018): 191–97. http://dx.doi.org/10.29252/jgit.6.2.191.

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47

Kumar Ghosh, Jayanta, and Upendra Nath Mishra. "Determination of Geoid Undulation by Astro-Geodetic Method." Journal of Surveying Engineering 142, no. 3 (August 2016): 05015007. http://dx.doi.org/10.1061/(asce)su.1943-5428.0000152.

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48

Gerstbach, Gottfried. "Precise alpine geoid determination without digital terrain models." Bulletin Géodésique 62, no. 4 (December 1988): 541–63. http://dx.doi.org/10.1007/bf02520243.

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49

Denker, H., and H. G. Wenzel. "Local geoid determination and comparison with GPS results." Bulletin Géodésique 61, no. 4 (December 1987): 349–66. http://dx.doi.org/10.1007/bf02520560.

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50

Dušátko, Drahomír. "On the determination of the European gravimetric geoid." Studia Geophysica et Geodaetica 36, no. 4 (December 1992): 392–93. http://dx.doi.org/10.1007/bf01625492.

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