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Assessment of ArcGIS based extraction of geoidal undulation compared to National Geospatial Intelligence Agency (NGA) model – A case study / Sher Muhammad in Journal of applied geodesy, vol 14 n° 1 (January 2020)  

Public [article]  inJournal of applied geodesy > vol 14 n° 1 (January 2020) . - pp 77 - 81 Titre : Assessment of ArcGIS based extraction of geoidal undulation compared to National Geospatial Intelligence Agency (NGA) model – A case study Type de document : Article/Communication Auteurs : Sher Muhammad, Auteur ; Lide Tian, Auteur Année de publication : 2020 Article en page(s) : pp 77 - 81 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] altitude orthométrique [Termes descripteurs IGN] détection d'erreur [Termes descripteurs IGN] Earth Gravity Model 1996 [Termes descripteurs IGN] ellipsoïde (géodésie) [Termes descripteurs IGN] géoïde altimétrique [Termes descripteurs IGN] Himalaya [Termes descripteurs IGN] interpolation [Termes descripteurs IGN] Matlab [Termes descripteurs IGN] modèle numérique de surface [Termes descripteurs IGN] niveau moyen des mers [Termes descripteurs IGN] Tibet Résumé : (auteur) Global Navigation Satellite System (GNSS) and remote sensing Digital Elevation Models (DEMs) represent earth’s surface elevation with reference to ellipsoid and orthometric heights. Proper estimation of the geoid (difference of ellipsoid and orthometric heights) is necessary before comparing data referenced to the different vertical datum. In this paper, an error in estimating EGM96 orthometric height is highlighted, verified by NGA/NASA developed model and MATLAB®. A significant error was found in the ArcGIS derived EGM96 orthometric heights range between ±6.9 meters. In addition, interpolation of low-resolution geoid data also produces significant biases depending on geographic location and the number of the interpolation data point. The bias was maximum negative in the central part of Tibetan Plateau and Himalaya. Therefore, estimation of orthometric height similar to NGA/NASA model precision is necessary for comparison of DEMs for natural resources management, 3D modelling and glaciers mass balance mainly in the mountainous regions. Numéro de notice : A2020-041 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1515/jag-2019-0030 En ligne : https://doi.org/10.1515/jag-2019-0030 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94512 [article]

Transformation 3D des coordonnées GPS en coordonnées Nord Sahara avec la MRE / Medjahed Sid Ahmed in Géomatique expert, n° 130-131 (octobre-novembre-décembre 2019)

Public [article]  inGéomatique expert > n° 130-131 (octobre-novembre-décembre 2019) . - pp 66 - 71 Titre : Transformation 3D des coordonnées GPS en coordonnées Nord Sahara avec la MRE Type de document : Article/Communication Auteurs : Medjahed Sid Ahmed, Auteur Année de publication : 2019 Article en page(s) : pp 66 - 71 Note générale : bibliographie Langues : Français (fre) Descripteur : [Vedettes matières IGN] Géodésie [Termes descripteurs IGN] Algérie [Termes descripteurs IGN] altitude orthométrique [Termes descripteurs IGN] ellipsoïde de Clarke [Termes descripteurs IGN] hauteur ellipsoïdale [Termes descripteurs IGN] Nord Sahara 1959 [Termes descripteurs IGN] régression multiple [Termes descripteurs IGN] système de référence altimétrique [Termes descripteurs IGN] transformation polynomiale [Termes descripteurs IGN] World Geodetic System 1984 Résumé : (éditeur) En Algérie tous les travaux cartographiques sont basés sur le système national NS59 (Nord Sahara 1959)et le référentiel altimétrique NGA (Nivellement général d'Algérie). Pour exploiter localement le GPS, il est essentiel de passer par les transformations entre systèmes de référence. Numéro de notice : A2019-588 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtSansCL DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94530 [article]

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
IFN-001-P002198	PER	Revue	Nogent-sur-Vernisson	Salle périodiques	Exclu du prêt

On determining orthometric heights from a corrector surface model based on leveling observations, GNSS, and a geoid model / Su-Kyung Kim in Journal of applied geodesy, vol 12 n° 4 (October 2018)  

Public [article]  inJournal of applied geodesy > vol 12 n° 4 (October 2018) . - pp 323 - 333 Titre : On determining orthometric heights from a corrector surface model based on leveling observations, GNSS, and a geoid model Type de document : Article/Communication Auteurs : Su-Kyung Kim, Auteur ; Jihye Park, Auteur ; Daniel T. Gillins, Auteur ; Michael Dennis, Auteur Année de publication : 2018 Article en page(s) : pp 323 - 333 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Nivellement [Termes descripteurs IGN] altitude orthométrique [Termes descripteurs IGN] coefficient de corrélation [Termes descripteurs IGN] compensation de coordonnées [Termes descripteurs IGN] erreur en position [Termes descripteurs IGN] géoïde gravimétrique [Termes descripteurs IGN] hauteur ellipsoïdale [Termes descripteurs IGN] North American Vertical Datum 1988 [Termes descripteurs IGN] Oregon (Etats-Unis) [Termes descripteurs IGN] système de référence altimétrique Résumé : (auteur) Leveling is a traditional geodetic surveying technique that has been used to realize a vertical datum. However, this technique is time consuming and prone to accumulate errors, where it relies on starting from one station with a known orthometric height. Establishing orthometric heights using Global Navigation Satellite Systems (GNSS) and a geoid model has been suggested [14], but this approach may involve less precisions than the direct measurements from leveling. In this study, an experimental study is presented to adjust the highly accurate leveling observations along with orthometric heights derived from GNSS observations and a geoid model. For the geoid model, the National Geodetic Survey’s gravimetric geoid model (TxGEOID16B) and hybrid geoid model (GEOID12B) were applied. Uncertainties in the leveled height differences, GNSS derived heights, and the geoid models were modeled, and a combined adjustment was implemented to construct the optimal combination of orthometric, ellipsoidal, and geoid height at each mark. As a result, the discrepancy from the published orthometric heights and the CSM (Corrector Surface Model) based adjusted orthometric heights with GEOID12B showed a mean and RMS of -8.5 mm and 16.6 mm, respectively, while TxGEOID16B had a mean and RMS of 28.9 mm and 34.6 mm, respectively. It should be emphasized that this approach was not influenced by the geodetic distribution of the stations where the correlation coefficients between the distance from the center of the surveying network and the discrepancy from the published heights using TxGEOID16B and GEOID12B are 0.03 and 0.36, respectively. Numéro de notice : 21435 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1515/jag-2018-0014 date de publication en ligne : 29/08/2018 En ligne : https://doi.org/10.1515/jag-2018-0014 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91004 [article]

Assessing the quality of GEOID12B model through field surveys / Ahmed F. Elaksher in Journal of applied geodesy, vol 12 n° 1 (January 2018)  

Public [article]  inJournal of applied geodesy > vol 12 n° 1 (January 2018) . - pp 1 - 14 Titre : Assessing the quality of GEOID12B model through field surveys Type de document : Article/Communication Auteurs : Ahmed F. Elaksher, Auteur ; Franck Kamtchang, Auteur ; Christian Wegmann, Auteur ; Adalberto Guerrero, Auteur Année de publication : 2018 Article en page(s) : pp 1 - 14 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] altitude orthométrique [Termes descripteurs IGN] anomalie de pesanteur [Termes descripteurs IGN] Etats-Unis [Termes descripteurs IGN] géoïde local [Termes descripteurs IGN] hauteur ellipsoïdale [Termes descripteurs IGN] quasi-géoïde Résumé : (auteur) Elevation differences have been determined through conventional ground surveying techniques for over a century. Since the mid-80s GPS, GLONASS and other satellite systems have modernized the means by which elevation differences are observed. In this article, we assessed the quality of GEIOD12B through long-occupation GNSS static surveys. A set of NGS benchmarks was occupied for at least one hour using dual-frequency GNSS receivers. Collected measurements were processed using a single CORS station at most 24 kilometers from the benchmarks. Geoid undulation values were driven by subtracting measured ellipsoidal heights from the orthometric heights posted on the NGS website. To assess the quality of GEOID12B, we compared our computed vertical shifts at the benchmarks with those estimated from GEOID12B published by NGS. In addition, Kriging model was used to interpolate local maps for the geoid undulations from the benchmark heights. The maps were compared with corresponding parts of GEOID12B. No biases were detected in the results and only shifts due to random errors were found. Discrepancies in the range of ten centimetres were noticed between our geoid undulation and the values available from NGS. Numéro de notice : A2018-013 Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/jag-2017-0013 En ligne : https://doi.org/10.1515/jag-2017-0013 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89092 [article]

On the geoid and orthometric height vs. quasigeoid and normal height / Lars E. Sjöberg in Journal of geodetic science, vol 8 n° 1 (January 2018)  

Public [article]  inJournal of geodetic science > vol 8 n° 1 (January 2018) . - pp 115 - 120 Titre : On the geoid and orthometric height vs. quasigeoid and normal height Type de document : Article/Communication Auteurs : Lars E. Sjöberg, Auteur Année de publication : 2018 Article en page(s) : pp 115 - 120 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] altitude normale [Termes descripteurs IGN] altitude orthométrique [Termes descripteurs IGN] géoïde [Termes descripteurs IGN] quasi-géoïde Résumé : (Auteur) The geoid, but not the quasigeoid, is an equipotential surface in the Earth’s gravity field that can serve both as a geodetic datum and a reference surface in geophysics. It is also a natural zero-level surface, as it agrees with the undisturbed mean sea level. Orthometric heights are physical heights above the geoid,while normal heights are geometric heights (of the telluroid) above the reference ellipsoid. Normal heights and the quasigeoid can be determined without any information on the Earth’s topographic density distribution, which is not the case for orthometric heights and geoid. We show from various derivations that the difference between the geoid and the quasigeoid heights, being of the order of 5 m, can be expressed by the simple Bouguer gravity anomaly as the only term that includes the topographic density distribution. This implies that recent formulas, including the refined Bouguer anomaly and a difference between topographic gravity potentials, do not necessarily improve the result. Intuitively one may assume that the quasigeoid, closely related with the Earth’s surface, is rougher than the geoid. For numerical studies the topography is usually divided into blocks of mean elevations, excluding the problem with a non-star shaped Earth. In this case the smoothness of both types of geoid models are affected by the slope of the terrain,which shows that even at high resolutions with ultra-small blocks the geoid model is likely as rough as the quasigeoid model. In case of the real Earth there are areas where the quasigeoid, but not the geoid, is ambiguous, and this problem increases with the numerical resolution of the requested solution. These ambiguities affect also normal and orthometric heights. However, this problem can be solved by using the mean quasigeoid model defined by using average topographic heights at any requested resolution. An exact solution of the ambiguity for the normal height/quasigeoid can be provided by GNSS-levelling. Numéro de notice : A2018-115 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1515/jogs-2018-0011 date de publication en ligne : 31/12/2018 En ligne : https://doi.org/10.1515/jogs-2018-0011 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92664 [article]

On the topographic bias and density distribution in modelling the geoid and orthometric heights / Lars E. Sjöberg in Journal of geodetic science, vol 8 n° 1 (January 2018)  

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On the estimation of physical height changes using GRACE satellite mission data – A case study of Central Europe / Walyeldeen Godah in Geodesy and cartography, vol 66 n° 2 (December 2017)  

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Evaluating the performance of using PPK-GPS technique in producing topographic contour map / Ahmed El Shouny in Marine geodesy, vol 40 n° 4 (July 2017)  

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Le chemin vers un système de référence altimétrique global et unifié / L. Sánchez in XYZ, n° 150 (mars - mai 2017)

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Détermination pratique de modèles de géoïde et autres surfaces de référence altimétrique / Jean-Louis Carme in XYZ, n° 150 (mars - mai 2017)

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Géoïde : mythe ou réalité ? / Françoise Duquenne in XYZ, n° 150 (mars - mai 2017)

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Evaluating the use of GPS heights in water conservation applications / Ahmed F. Elaksher in Survey review, vol 48 n° 348 (May 2016)  

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Development of new hybrid geoid model for Japan, "GSIGEO2011" / Basara Miyahara in Bulletin of the GeoSpatial Information authority of Japan, vol 62 (December 2014)

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CIRCE RHONE : mise en place d'une grille de transformation altimétrique entre les altitudes orthométriques (NGF/Lallemand) et normales (NGF/IGN69) / Paul-Henri Faure in XYZ, n° 134 (mars - mai 2013)

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Utilisation de la technique du nivellement par GPS pour l'élaboration des surfaces de conversions altimétriques / S. Medjahed in Bulletin des sciences géographiques, n° 26 (octobre 2011)

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