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On the importance of accurately ray-traced troposphere corrections for interferometric SAR data / T. Hobiger in Journal of geodesy, vol 84 n° 9 (September 2010)  

Public [article]  inJournal of geodesy > vol 84 n° 9 (September 2010) . - pp 537 - 546 Titre : On the importance of accurately ray-traced troposphere corrections for interferometric SAR data Type de document : Article/Communication Auteurs : T. Hobiger, Auteur ; S. Kinoshita, Auteur ; S. Shimizu, Auteur ; et al., Auteur Année de publication : 2010 Article en page(s) : pp 537 - 546 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s) [Termes IGN] correction troposphérique [Termes IGN] interféromètrie par radar à antenne synthétique [Termes IGN] lancer de rayons [Termes IGN] modèle atmosphérique [Termes IGN] propagation troposphérique Résumé : (Auteur) Numerical weather models offer the possibility to compute corrections for a variety of space geodetic applications, including remote sensing techniques like interferometric SAR. Due to the computational complexity, exact ray-tracing is avoided in many cases and mapping approaches are applied to transform vertically integrated delay corrections into slant direction. Such an approach works well as long as lateral atmospheric gradients are small enough to be neglected. But since such an approximation holds only for very rare cases it is investigated how horizontal gradients of different atmospheric constituents can evoke errors caused by the mapping strategy. Moreover, it is discussed how sudden changes of wet refractivity can easily lead to millimeter order biases when simplified methods are applied instead of ray-tracing. By an example, based on real InSAR data, the differences of the various troposphere correction schemes are evaluated and it is shown how the interpretation of the geophysical signals can be affected. In addition, it is studied to which extend troposphere noise can be reduced by applying the exact ray-tracing solution. Numéro de notice : A2010-414 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-010-0393-3 Date de publication en ligne : 11/06/2010 En ligne : https://doi.org/10.1007/s00190-010-0393-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30607 [article]

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266-2010091	SL	Revue	Centre de documentation	Revues en salle	Disponible

Combining EGM2008 and SRTM/DTM2006.0 residual terrain model data to improve quasigeoid computations in mountainous areas devoid of gravity data / C. Hirt in Journal of geodesy, vol 84 n° 9 (September 2010)  

Public [article]  inJournal of geodesy > vol 84 n° 9 (September 2010) . - pp 557 - 567 Titre : Combining EGM2008 and SRTM/DTM2006.0 residual terrain model data to improve quasigeoid computations in mountainous areas devoid of gravity data Type de document : Article/Communication Auteurs : C. Hirt, Auteur ; Will E. Featherstone, Auteur ; Urs Marti, Auteur Année de publication : 2010 Article en page(s) : pp 557 - 567 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] Alpes [Termes IGN] champ de pesanteur terrestre [Termes IGN] Earth Gravity Model 2008 [Termes IGN] géoïde terrestre [Termes IGN] modèle de géopotentiel [Termes IGN] modèle numérique de terrain [Termes IGN] montagne [Termes IGN] résidu Résumé : (Auteur) A global geopotential model, like EGM2008, is not capable of representing the high-frequency components of Earth’s gravity field. This is known as the omission error. In mountainous terrain, omission errors in EGM2008, even when expanded to degree 2,190, may reach amplitudes of 10 cm and more for height anomalies. The present paper proposes the utilisation of high-resolution residual terrain model (RTM) data for computing estimates of the omission error in rugged terrain. RTM elevations may be constructed as the difference between the SRTM (Shuttle Radar Topography Mission) elevation model and the DTM2006.0 spherical harmonic topographic expansion. Numerical tests, carried out in the German Alps with a precise gravimetric quasigeoid model (GCG05) and GPS/levelling data as references, demonstrate that RTM-based omission error estimates improve EGM2008 height anomaly differences by 10 cm in many cases. The comparisons of EGM2008-only height anomalies and the GCG05 model showed 3.7 cm standard deviation after a bias-fit. Applying RTM omission error estimates to EGM2008 reduces the standard deviation to 1.9 cm which equates to a significant improvement rate of 47%. Using GPS/levelling data strongly corroborates these findings with an improvement rate of 49%. The proposed RTM approach may be of practical value to improve quasigeoid determination in mountainous areas without sufficient regional gravity data coverage, e.g., in parts of Asia, South America or Africa. As a further application, RTM omission error estimates will allow refined validation of global gravity field models like EGM2008 from GPS/levelling data. Numéro de notice : A2010-415 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-010-0395-1 Date de publication en ligne : 03/07/2010 En ligne : https://doi.org/10.1007/s00190-010-0395-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30608 [article]

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Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2010091	SL	Revue	Centre de documentation	Revues en salle	Disponible

Integer ambiguity resolution in precise point positionning : method comparison / J. Geng in Journal of geodesy, vol 84 n° 9 (September 2010)  

Public [article]  inJournal of geodesy > vol 84 n° 9 (September 2010) . - pp 569 - 581 Titre : Integer ambiguity resolution in precise point positionning : method comparison Type de document : Article/Communication Auteurs : J. Geng, Auteur ; X. Meng, Auteur ; A. Dodson, Auteur ; Felix Norman Teferle, Auteur Année de publication : 2010 Article en page(s) : pp 569 - 581 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] ambiguïté entière [Termes IGN] analyse comparative [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] précision millimétrique [Termes IGN] résolution d'ambiguïté Résumé : (Auteur) Integer ambiguity resolution at a single receiver can be implemented by applying improved satellite products where the fractional-cycle biases (FCBs) have been separated from the integer ambiguities in a network solution. One method to achieve these products is to estimate the FCBs by averaging the fractional parts of the float ambiguity estimates, and the other is to estimate the integer-recovery clocks by fixing the undifferenced ambiguities to integers in advance. In this paper, we theoretically prove the equivalence of the ambiguity-fixed position estimates derived from these two methods by assuming that the FCBs are hardware-dependent and only they are assimilated into the clocks and ambiguities. To verify this equivalence, we implement both methods in the Position and Navigation Data Analyst software to process 1 year of GPS data from a global network of about 350 stations. The mean biases between all daily position estimates derived from these two methods are only 0.2, 0.1 and 0.0 mm, whereas the standard deviations of all position differences are only 1.3, 0.8 and 2.0 mm for the East, North and Up components, respectively. Moreover, the differences of the position repeatabilities are below 0.2 mm on average for all three components. The RMS of the position estimates minus those from the International GNSS Service weekly solutions for the former method differs by below 0.1 mm on average for each component from that for the latter method. Therefore, considering the recognized millimeter-level precision of current GPS-derived daily positions, these statistics empirically demonstrate the theoretical equivalence of the ambiguity-fixed position estimates derived from these two methods. In practice, we note that the former method is compatible with current official clock-generation methods, whereas the latter method is not, but can potentially lead to slightly better positioning quality. Numéro de notice : A2010-416 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-010-0399-x Date de publication en ligne : 06/08/2010 En ligne : https://doi.org/10.1007/s00190-010-0399-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30609 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2010091	SL	Revue	Centre de documentation	Revues en salle	Disponible