Centre dedocumentation
scientifique

Prediction of vertical deflections from high-degree spherical harmonic synthesis and residual terrain model data / C. Hirt in Journal of geodesy, vol 84 n° 3 (March 2010)  

Public [article]  inJournal of geodesy > vol 84 n° 3 (March 2010) . - pp 179 - 190 Titre : Prediction of vertical deflections from high-degree spherical harmonic synthesis and residual terrain model data Type de document : Article/Communication Auteurs : C. Hirt, Auteur Année de publication : 2010 Article en page(s) : pp 179 - 190 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] Allemagne [Termes IGN] Alpes centrales [Termes IGN] champ de pesanteur terrestre [Termes IGN] déviation de la verticale [Termes IGN] Earth Gravity Model 2008 [Termes IGN] harmonique sphérique [Termes IGN] MNS SRTM [Termes IGN] modèle de géopotentiel [Termes IGN] modèle de géopotentiel local [Termes IGN] modèle numérique de terrain [Termes IGN] Suisse [Termes IGN] valeur efficace Résumé : (Auteur) This study demonstrates that in mountainous areas the use of residual terrain model (RTM) data significantly improves the accuracy of vertical deflections obtained from high-degree spherical harmonic synthesis. The new Earth gravitational model EGM2008 is used to compute vertical deflections up to a spherical harmonic degree of 2,160. RTM data can be constructed as difference between high-resolution Shuttle Radar Topography Mission (SRTM) elevation data and the terrain model DTM2006.0 (a spherical harmonic terrain model that complements EGM2008) providing the long-wavelength reference surface. Because these RTM elevations imply most of the gravity field signal beyond spherical harmonic degree of 2,160, they can be used to augment EGM2008 vertical deflection predictions in the very high spherical harmonic degrees. In two mountainous test areas—the German and the Swiss Alps—the combined use of EGM2008 and RTM data was successfully tested at 223 stations with high-precision astrogeodetic vertical deflections from recent zenith camera observations (accuracy of about 0.1 arc seconds) available. The comparison of EGM2008 vertical deflections with the ground-truth astrogeodetic observations shows root mean square (RMS) values (from differences) of 3.5 arc seconds for È and 3.2 arc seconds for È , respectively. Using a combination of EGM2008 and RTM data for the prediction of vertical deflections considerably reduces the RMS values to the level of 0.8 arc seconds for both vertical deflection components, which is a significant improvement of about 75%. Density anomalies of the real topography with respect to the residual model topography are one factor limiting the accuracy of the approach. The proposed technique for vertical deflection predictions is based on three publicly available data sets: (1) EGM2008, (2) DTM2006.0 and (3) SRTM elevation data. This allows replication of the approach for improving the accuracy of EGM2008 vertical deflection predictions in regions with a rough topography or for improved validation of EGM2008 and future high-degree spherical harmonic models by means of independent ground truth data. Numéro de notice : A2010-156 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-009-0354-x Date de publication en ligne : 12/11/2009 En ligne : https://doi.org/10.1007/s00190-009-0354-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30351 [article]

Réservation

Réserver ce document

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2010031	SL	Revue	Centre de documentation	Revues en salle	Disponible

Accuracy of airborne lidar derived elevation: empirical assessment and error budget / M.E. Hodgson in Photogrammetric Engineering & Remote Sensing, PERS, vol 70 n° 3 (March 2004)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 70 n° 3 (March 2004) . - pp 331 - 339 Titre : Accuracy of airborne lidar derived elevation: empirical assessment and error budget Type de document : Article/Communication Auteurs : M.E. Hodgson, Auteur ; P. Bresnahan, Auteur Année de publication : 2004 Article en page(s) : pp 331 - 339 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s) [Termes IGN] altitude [Termes IGN] ALTM [Termes IGN] cartographie topographique [Termes IGN] données lidar [Termes IGN] GPS en mode statique [Termes IGN] précision géométrique (imagerie) [Termes IGN] utilisation du sol [Termes IGN] valeur efficace Résumé : (Auteur) As part of a countywide large-scale mapping effort for Richland County, South Carolina, an accuracy assessment of a recently acquired lidar-derived data set was conducted. Airborne lidar (2m nominal posting) was collected at a flying height of 1207 meters above ground level (AGL) using an Optech ALTM (Airborne Laser Terrain Mapper) 1210 system. Unique to this study are the reference point elevations. Rather than using an interpolation approach for gathering observed elevations at reference points, the x-y coordinates of lidar points were located in the field and these elevations were surveyed. Using both total-station-based and rapid-static GPS techniques, observed vertical heights were measured at each reference lidar posting. The variability of vertical accuracy was evaluated for six land-cover categories. Root-mean-squared error (RmsE) values ranged from a low of 17 to 19 cm (pavement, low grass, and evergreen forests) to a high of 26 cm (deciduous forests). The unique error assessment of lidar postings also allowed for the creation of an error budget model. The observed lidar elevation error was decomposed into errors from lidar system measurements, horizontal displacement, interpolation error, and surveyor error. A cross-validation approach was used to assess the observed interpolated lidar elevation error for each field-verified reference point. In order of decreasing importance, the lidar system measurements were the dominant source of error-followed by interpolation error, horizontal displacement error, and surveyor error. Observed elevation error in steeper slopes (e.g., 25°) was estimated to be twice as large as those on low slopes (e.g., 1.5°). Copyright ASPRS Numéro de notice : A2004-103 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.70.3.331 En ligne : https://doi.org/10.14358/PERS.70.3.331 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26630 [article]

Optimizing a network-based RTK method for OTF [on-the-fly] positioning / L.P. Fortes in GPS solutions, vol 7 n° 2 (August 2003)  

Public [article]  inGPS solutions > vol 7 n° 2 (August 2003) . - pp 61 - 73 Titre : Optimizing a network-based RTK method for OTF [on-the-fly] positioning Type de document : Article/Communication Auteurs : L.P. Fortes, Auteur ; M.E. Cannon, Auteur ; et al., Auteur Année de publication : 2003 Article en page(s) : pp 61 - 73 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] covariance [Termes IGN] erreur [Termes IGN] filtre de Kalman [Termes IGN] ionosphère [Termes IGN] méthode des moindres carrés [Termes IGN] optimisation (mathématiques) [Termes IGN] orbite [Termes IGN] positionnement cinématique en temps réel [Termes IGN] précision centimétrique [Termes IGN] résolution d'ambiguïté [Termes IGN] station de référence [Termes IGN] valeur efficace Résumé : (Auteur) Differential GPS is able to provide cm-level positoning accuracies, as long as the carrier phase ambiguities are resolved to integer values. Classical methods are based on the use of a single reference station located in the vicinity of the rover. Due to the spatial decorrelation of the errors, the distance between the reference station and the user is generally limited to within 20-30 km or even less, mainly due to the ionosphere. The MultiRef method, developed at the University of Calgary, uses a network of reference stations to generate regional code and carrier phase corrections, which can be transmitted to users in order to increase the distance over which integer ambiguity resolution is possible. In the original method, the correlated errors, due to the satellite orbits, troposphere, and ionosphere are modeled together using the L1 and wide-lane observables. In this paper extensive efforts were carried out towards as optimizing the MultiRef method with the objective of maximizing its performance. Data collected in southeastern Brazil was used in this research. At first, the impact of using covariance function calculated with different data sets was assessed, showing improvement variations of up to 14% in the observation domain compared to using no network corrections, with the exact improvement depending on the data set used in the computation. A new approach, also using least-squares prediction (collation), was proposed to separately model the correlated errors. An additional effort was carried out in the terms of modeling the ionosphere into directional components. Results of the enhanced method showed the same level of improvement as those obtained using the original covariance functions. However, this new approach has advantages with respect to the transmission of the corrections. Finally, an additional step was taken in terms of applying a Kalman filter to the corrections in order to improve their quality. For cases when the corresponding satellite was setting at low elevations, the filter approach improved results up to 44%. A study on the impact of the various covariance functions on the estimated accuracy of the corrections is also included. Numéro de notice : A2003-370 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-003-0054-6 En ligne : https://doi.org/10.1007/s10291-003-0054-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=26450 [article]

Réservation

Réserver ce document

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
026-03031	RAB	Revue	Centre de documentation	En réserve 3L	Disponible

Artificial neural networks as a method of spatial interpolation for digital elevation models / D.A. Merwin in Cartography and Geographic Information Science, vol 29 n° 2 (April 2002)  

Public [article]  inCartography and Geographic Information Science > vol 29 n° 2 (April 2002) . - pp 99 - 110 Titre : Artificial neural networks as a method of spatial interpolation for digital elevation models Type de document : Article/Communication Auteurs : D.A. Merwin, Auteur ; R.G. Cromley, Auteur ; Daniel L. Civco, Auteur Année de publication : 2002 Article en page(s) : pp 99 - 110 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes d'information géographique [Termes IGN] interpolation inversement proportionnelle à la distance [Termes IGN] interpolation spatiale [Termes IGN] modèle numérique de surface [Termes IGN] réseau neuronal artificiel [Termes IGN] valeur efficace Résumé : (Auteur) This paper examines the performance of artificial neural networks (ANNs) as a method of spatial interpolation, when presented with irregular and regular samples of elevation data. The results of the ANN interpolation are compared with results obtained by kriging. Tests of spatial bias in the systematic errors contained in each of the neural network-derived DEMs were conducted using four attributes: slope, aspect, average direction and average distance from the nearest sampled value. Based on RMS and other evaluation measures, the accuracy of estimated DEMs from regular and irregular sample distributions using neural networks is lower than the accuracy level derived from kriging. The accuracy level of the ANN interpolators also decreases as the range of elevation values in DEMs increases. As reported in the literature, ANNs are approximate interpolators, and the pattern of under-prediction and over-prediction of elevation values in this study revealed that all estimated values fell within the range of sample elevations. Neural networks cannot predict values outside the range of elevation values contained in the sample, a property shared by other interpolators such as inverse weighted distance. Numéro de notice : A2002-144 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1559/152304002782053323 En ligne : https://doi.org/10.1559/152304002782053323 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22059 [article]

Réservation

Réserver ce document

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
032-02021	RAB	Revue	Centre de documentation	En réserve 3L	Disponible

Delay-Doppler analysis of bistatically reflected signals from the ocean surface: theory and application / T. Elfouhaily in IEEE Transactions on geoscience and remote sensing, vol 40 n° 3 (March 2002)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 40 n° 3 (March 2002) . - pp 560 - 573 Titre : Delay-Doppler analysis of bistatically reflected signals from the ocean surface: theory and application Type de document : Article/Communication Auteurs : T. Elfouhaily, Auteur ; D.R. Thompson, Auteur ; L. Linstrom, Auteur Année de publication : 2002 Article en page(s) : pp 560 - 573 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] données Doppler [Termes IGN] mesurage d'effet Doppler [Termes IGN] réflexion (rayonnement) [Termes IGN] surface de la mer [Termes IGN] trajet multiple [Termes IGN] valeur efficace Résumé : (Auteur) We present a new stochastic theory for delay-Doppler mapping of the ocean surface for bistatic scattering. This stochastic theory should complement nicely the previous theories for the Global Positioning System (GPS) reflected signals from ocean surfaces, especially that of Zavorotny and Voronovich. We quantify the Doppler spread of the reflected signal before interpreting the delay. Our theoretical results compare very well to Doppler spectra computed using data collected during an airborne campaign. The bandwidth of the spectra is linked to the geometry and to the ocean roughness. The bulk of the Doppler spread is caused by the rms slope and not by the surface orbital velocity. Our stochastic theory is generalized to include the delay mapping made possible by the existence of the pseudorandom noise code on the GPS L-band carrier. These results can be seen as a generalization of Woodward's theorem for FM signals to delay-Doppler analysis of more complicated signals. Our formulation is amenable to inversion for the determination of geophysical parameters such as surface wind vector and mean sea level. Another novelty in our approach is the inclusion of the sea state. Numéro de notice : A2002-175 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2002.1000316 En ligne : https://doi.org/10.1109/TGRS.2002.1000316 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22090 [article]

Réservation

Réserver ce document

Exemplaires (2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
065-02031	RAB	Revue	Centre de documentation	En réserve 3L	Disponible
065-02032	RAB	Revue	Centre de documentation	En réserve 3L	Disponible

Saisie de la couverture neigeuse de sites avalancheux par des systèmes aéroportés / Julien Vallet (2002)  

Permalink

Simultane Neuausgleichung des globalen 3D-Mars-Netzes / W. Zeitler (1999)

Permalink

Improved recovery of gravity anomalies from dense altimeter data / J.H. Kim (1996)

Permalink

Estimation of sea dynamic topography, ocean tides, and secular changes from Topex altimeter data / Y.M. Wang (1994)

Permalink

The first low Earth orbiter with precise GPS positioning, Topex-Poseidon / Willy I. Bertiger (1994)

Permalink

The determination of the orbit of the Japanese satellite "AJISAI" and the GEM-T1 and GEM-T2 gravity field models / B.V. Sanchez (1990)

Permalink