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Multi-technique comparison of tropospheric zenith delays derived during the CONT02 campaign / Pascal Willis in Journal of geodesy, vol 79 n° 10-11 (February 2006)
[article]
Titre : Multi-technique comparison of tropospheric zenith delays derived during the CONT02 campaign Type de document : Article/Communication Auteurs : Pascal Willis , Auteur ; K. Snajdrova, Auteur ; Johannes Böhm , Auteur ; Rüdiger Haas, Auteur Année de publication : 2006 Article en page(s) : pp 613 - 623 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] analyse comparative
[Termes IGN] distance zénithale
[Termes IGN] données WVR
[Termes IGN] écart type
[Termes IGN] erreur systématique
[Termes IGN] météorologie
[Termes IGN] positionnement par DORIS
[Termes IGN] positionnement par GPS
[Termes IGN] prévision météorologique
[Termes IGN] propagation troposphérique
[Termes IGN] traitement du signal
[Termes IGN] troposphèreRésumé : (Auteur) In October 2002, 15 continuous days of Very Long Baseline Interferometry (VLBI) data were observed in the Continuous VLBI 2002 (CONT02) campaign. All eight radio telescopes involved in CONT02 were co-located with at least one other space-geodetic technique, and three of them also with a Water Vapor Radiometer (WVR). The goal of this paper is to compare the tropospheric zenith delays observed during CONT02 by VLBI, Global Positioning System (GPS), Doppler Orbitography Radiopositioning Integrated by Satellite (DORIS) and WVR and te, compare them also with operational pressure level data from the European Centre for Medium-Range Weather Forecasts (ECMWF). We show that the tropospheric zenith delays from VLBI and GPS are in good agreement at the 3-7 mm level. However, while only small biases can be found for most of the stations, at Kokee Park (Hawaii, USA) and Westford (Massachusetts, USA) the zenith delays derived by GPS are larger by more than 5 mm than those from VLBI. At three of the four DORIS stations, there is also a fairly good agreement with GPS and VLBI (about 10 mm), but at Kokee Park the agreement is only at about 30 mm standard deviation, probably due to the much older installation and type of DORIS equipment. This comparison also allows testing of different DORIS analysis strategies with respect to their real impact on the precision of the derived tropospheric parameters. Ground truth information about the zenith delays can also be obtained from the ECMWF numerical weather model and at three sites using WVR measurements, allowing for comparisons with results from the space-geodetic techniques. While there is a good agreement (with some problems mentioned above about DORIS) among the space-geodetic techniques, the comparison with WVR and ECMWF is at a lower accuracy level. The complete CONT02 data set is sufficient to derive a good estimate of the actual precision and accuracy of each geodetic technique for applications in meteorology. Numéro de notice : A2006-088 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-005-0010-z En ligne : https://doi.org/10.1007/s00190-005-0010-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27815
in Journal of geodesy > vol 79 n° 10-11 (February 2006) . - pp 613 - 623[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-06011 RAB Revue Centre de documentation En réserve L003 Disponible 266-06012 RAB Revue Centre de documentation Revues en salle Disponible A new approach to the nearest-neighbour method to discover cluster features in overlaid spatial point processes / Tao Pei in International journal of geographical information science IJGIS, vol 20 n° 2 (february 2006)
[article]
Titre : A new approach to the nearest-neighbour method to discover cluster features in overlaid spatial point processes Type de document : Article/Communication Auteurs : Tao Pei, Auteur ; A - Xing Zhu, Auteur ; et al., Auteur Année de publication : 2006 Article en page(s) : pp 153 - 168 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image
[Termes IGN] Chine
[Termes IGN] classification barycentrique
[Termes IGN] distribution de Poisson
[Termes IGN] filtrage du bruit
[Termes IGN] groupe
[Termes IGN] regroupement de données
[Termes IGN] segmentation d'image
[Termes IGN] séisme
[Termes IGN] variation de densitéRésumé : (Auteur) When two spatial point processes are overlaid, the one with the higher rate is shown as clustered points, and the other one with the lower rate is often perceived to be background. Usually, we consider the clustered points as feature and the background as noise. Revealing these point clusters allows us to further examine and understand the spatial point process. Two important aspects in discerning spatial cluster features from a set of points are the removal of noise and the determination of the number of spatial clusters. Until now, few methods were able to deal with these two aspects at the same time in an automated way. In this study, we combine the nearest-neighbour (NN) method and the concept of density-connected to address these two aspects. First, the removal of noise can be achieved using the NN method; then, the number of clusters can be determined by finding the density-connected clusters. The complexity for finding density connected clusters is reduced in our algorithm. Since the number of clusters depends on the value of k (the kth nearest neighbour), we introduce the concept of lifetime for the number of clusters in order to measure how stable the segmentation results (or number of clusters) are. The number of clusters with the longest lifetime is considered to be the final number of clusters. Finally, a seismic example of the west part of China is used as a case study to examine the validity of our method. In this seismic case study, we discovered three seismic clusters: one as the foreshocks of the Songpan quake (M=7.2), and the other two as aftershocks related to the Kangding-Jiulong (M=6.2) quake and Daguan quake (M= 7. 1), respectively. Through this case study, we conclude that the approach we proposed is effective in removing noise and determining the number of feature clusters. Numéro de notice : A2006-065 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1080/13658810500399654 En ligne : https://doi.org/10.1080/13658810500399654 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27792
in International journal of geographical information science IJGIS > vol 20 n° 2 (february 2006) . - pp 153 - 168[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 079-06021 RAB Revue Centre de documentation En réserve L003 Disponible 079-06022 RAB Revue Centre de documentation En réserve L003 Disponible Spatiotriangulation with multisensor HR stereo-images / Thierry Toutin in IEEE Transactions on geoscience and remote sensing, vol 44 n° 2 (February 2006)
[article]
Titre : Spatiotriangulation with multisensor HR stereo-images Type de document : Article/Communication Auteurs : Thierry Toutin , Auteur Année de publication : 2006 Article en page(s) : pp 456 - 462 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Photogrammétrie spatiale
[Termes IGN] compensation par faisceaux
[Termes IGN] compensation par moindres carrés
[Termes IGN] données multicapteurs
[Termes IGN] erreur moyenne quadratique
[Termes IGN] géoréférencement
[Termes IGN] image Ikonos
[Termes IGN] image Quickbird
[Termes IGN] image SPOT-HRG
[Termes IGN] image SPOT-HRS
[Termes IGN] modèle stéréoscopique
[Termes IGN] point de vérification
[Termes IGN] points homologues
[Termes IGN] précision géométrique (imagerie)
[Termes IGN] spatiotriangulationRésumé : (Auteur) The objective of this research study was to evaluate the spatiotriangulation applied to multiltisensor high-resolution satellite stereo-images, which enabled the simultaneous geometric processing of a large number of stereo-pairs together to reduce the control point requirement. The spatiotriangulation is based on the three-dimensional physical models developed for multisensor images at the Canada Centre for Remote Sensing, Natural Resources Canada and on a least squares block stereo-bundle adjustment process with orbital constraints. The spatiotriangulation was applied to five along-/across-track stereo-images [panchromatic Systeme Pour l'Observation de la Terre 5 (SPOT-5) High-Resolution-Stereoscopy (HRS) and High-Resolution-Geometry (HRG), Ikonos, and QuickBird] acquired over Quebec, Canada. The first results of stereo/block bundle adjustment showed that the same error residuals than the input data errors (1/2 to 1-2 pixels) were obtained depending of the stereo-images, whether independently or simultaneously processed. The second and most important results were related to simultaneous stereo-bundle adjustments of the largest "master" SPOT-5 stereo-pair (either HRS or HRG) using 12 ground control points (GCPs) and the smallest "slave" stereo-pair(s) using no GCP but only stereo tie-points (TPs). Better results were normally obtained with SPOT-5-HRG (5-m resolution) as the "master" stereo-pair due to less difference in the sensors resolution than with SPOT-5 HRS. The root mean square errors, verified by independent check points (ICPs) belonging only to the "slave" stereo-pairs, were around 2 in in the three axes. However, the combined image pointing and map errors of ICPs (1-2 m) are included in these 2-m error results, and the internal accuracy of the stereo-pairs should thus be better (less than one resolution). The research study demonstrated thus the possibility to use the largest stereo-pair with a reduced number of GCPs to simultaneously adjust single or multiple stereo-pair(s) with only stereo TPs, and with no degradation in the accuracy. Numéro de notice : A2006-127 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2005.861005 En ligne : https://doi.org/10.1109/TGRS.2005.861005 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27854
in IEEE Transactions on geoscience and remote sensing > vol 44 n° 2 (February 2006) . - pp 456 - 462[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 065-06021 RAB Revue Centre de documentation En réserve L003 Disponible Systematic errors in the Z-geocenter derived using satellite tracking data: a case study from SPOT-4 DORIS data in 1998 / Pascal Willis in Journal of geodesy, vol 79 n° 10-11 (February 2006)
[article]
Titre : Systematic errors in the Z-geocenter derived using satellite tracking data: a case study from SPOT-4 DORIS data in 1998 Type de document : Article/Communication Auteurs : Pascal Willis , Auteur ; Jean-Paul Berthias, Auteur ; Yoaz E. Bar-Sever, Auteur Année de publication : 2006 Article en page(s) : pp 567 - 572 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] données DORIS
[Termes IGN] erreur systématique
[Termes IGN] géocentre
[Termes IGN] orbitographie
[Termes IGN] positionnement par DORIS
[Termes IGN] poursuite de satelliteRésumé : (Auteur) Within the scope of the Global Geodetic Observing System, Doppler Orbit Determination and Radiopositioning Integrated by Satellite - as a geodetic technique - can provide precise and continuous monitoring of the geocenter motion related to mass redistribution in the Earth, ocean and atmosphere system. We have reanalyzed 1998 DORIS/SPOT-4 (Satellite pour l'Observation de la Terre) data that were previously generating inconsistent geocenter positions (-65 cm offset). We show here that this error is due to an incorrect phase center correction provided with the DORIS preprocessed data resulting from a +12cm offset in the cross-track direction that has been confirmed since. We also conclude that a 1 mm error in the cross-track offset of non-yawing sun-synchronous SPOT satellites will generate a -6.5 mm error in the derived Z-geocenter. Other non-yawing satellites would also be affected by a similar effect whose amplitude could be easily estimated from the orbit inclination. Numéro de notice : A2006-086 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-005-0013-9 En ligne : https://doi.org/10.1007/s00190-005-0013-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27813
in Journal of geodesy > vol 79 n° 10-11 (February 2006) . - pp 567 - 572[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 266-06011 RAB Revue Centre de documentation En réserve L003 Disponible 266-06012 RAB Revue Centre de documentation Revues en salle Disponible The accuracy of grid digital elevation models linearly constructed from scattered sample data / F. Aguilar in International journal of geographical information science IJGIS, vol 20 n° 2 (february 2006)
[article]
Titre : The accuracy of grid digital elevation models linearly constructed from scattered sample data Type de document : Article/Communication Auteurs : F. Aguilar, Auteur ; M. Aguilar, Auteur ; et al., Auteur Année de publication : 2006 Article en page(s) : pp 169 - 192 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Photogrammétrie numérique
[Termes IGN] couple stéréoscopique
[Termes IGN] écart type
[Termes IGN] échantillonnage de données
[Termes IGN] erreur d'échantillon
[Termes IGN] erreur moyenne quadratique
[Termes IGN] image aérienne
[Termes IGN] interpolation linéaire
[Termes IGN] maille carrée
[Termes IGN] modèle numérique de surface
[Termes IGN] modélisation 3D
[Termes IGN] pente
[Termes IGN] propagation d'erreur
[Termes IGN] rugosité du sol
[Termes IGN] système d'information géographiqueRésumé : (Auteur) In this paper, a theoretical-empirical model is developed for modelling the accuracy of a grid digital elevation model (DEM) linearly constructed from scattered sample data. The theoretical component integrates sample data accuracy in the model by means of the error-propagation theory. The empirical component seeks to model what is known as information loss, i.e. the sum of the error due purely to sampling the continuous terrain surface with a finite grid interval and the interpolation error. For this purpose, randomly spaced data points, supposed to be free of error, were converted into regularly gridded data points using triangulation with linear interpolation. Original sample data were collected with a 2 x 2 m sampling interval from eight different morphologies, from flat terrain to highly rugged terrain, applying digital photogrammetric methods to large-scale aerial stereo imagery (1 :5000). The DEM root mean square error was calculated by the true validation method over several sets of check points, obtaining the different sampling densities tested in this work. Several empirical models are calibrated and validated with the experimental data set by modelling the DEM accuracy by combining two variables such as sampling density and a descriptive attribute of terrain morphology. These empirical models presented a morphology based on the product of two potential functions, one related to the terrain roughness and another related to the sampling density. The terrain descriptors tested were average terrain slope, standard deviation of terrain slope, standard deviation of unitary vectors perpendicular to the topographic surface (SDUV), standard deviation of the difference in height between adjacent samples in the grid DEM (SDHD), and roughness estimation by first-, second-, or third-degree surface fitting error. The values obtained for those terrain descriptors were reasonably independent from the number and spatial distribution of the sample data. The models based on descriptors SDHD, SDUV, and standard deviation of slope provided a good fitting to the data observed (R 2> 0.94) in the calibration phase, model SDHD being the one that yielded the best results in validation. Therefore, it would be possible to establish a priori the optimum grid size required to generate or store a DEM of a particular accuracy, with the saving in computing time and file size that this would mean for the digital flow of the mapping information in GIS. Numéro de notice : A2006-066 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1080/13658810500399670 En ligne : https://doi.org/10.1080/13658810500399670 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27793
in International journal of geographical information science IJGIS > vol 20 n° 2 (february 2006) . - pp 169 - 192[article]Réservation
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