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A synergy method to improve ensemble weather predictions and differential SAR interferograms / Franz-Georg Ulmer in ISPRS Journal of photogrammetry and remote sensing, vol 109 (November 2015)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 109 (November 2015) . - pp 98 - 107 Titre : A synergy method to improve ensemble weather predictions and differential SAR interferograms Type de document : Article/Communication Auteurs : Franz-Georg Ulmer, Auteur ; Nico Adam, Auteur Année de publication : 2015 Article en page(s) : pp 98 - 107 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] correction différentielle [Termes IGN] effet atmosphérique [Termes IGN] équation différentielle [Termes IGN] image radar moirée [Termes IGN] interferométrie différentielle [Termes IGN] interféromètrie par radar à antenne synthétique [Termes IGN] Pays-Bas [Termes IGN] prévision météorologique Résumé : (auteur) A compensation of atmospheric effects is essential for mm-sensitivity in differential interferometric synthetic aperture radar (DInSAR) techniques. Numerical weather predictions are used to compensate these disturbances allowing a reduction in the number of required radar scenes. Practically, predictions are solutions of partial differential equations which never can be precise due to model or initialisation uncertainties. In order to deal with the chaotic nature of the solutions, ensembles of predictions are computed. From a stochastic point of view, the ensemble mean is the expected prediction, if all ensemble members are equally likely. This corresponds to the typical assumption that all ensemble members are physically correct solutions of the set of partial differential equations. DInSAR allows adding to this knowledge. Observations of refractivity can now be utilised to check the likelihood of a solution and to weight the respective ensemble member to estimate a better expected prediction. The objective of the paper is to show the synergy between ensemble weather predictions and differential interferometric atmospheric correction. We demonstrate a new method first to compensate better for the atmospheric effect in DInSAR and second to estimate an improved numerical weather prediction (NWP) ensemble mean. Practically, a least squares fit of predicted atmospheric effects with respect to a differential interferogram is computed. The coefficients of this fit are interpreted as likelihoods and used as weights for the weighted ensemble mean. Finally, the derived weighted prediction has minimal expected quadratic errors which is a better solution compared to the straightforward best-fitting ensemble member. Furthermore, we propose an extension of the algorithm which avoids the systematic bias caused by deformations. It makes this technique suitable for time series analysis, e.g. persistent scatterer interferometry (PSI). We validate the algorithm using the well known Netherlands-DInSAR test case and first show that the atmospheric compensation improves by nearly 40% compared to the straightforward technique. Second, we compare our results with independent sea level pressure data. In our test case, the mean squared error is reduced by 29% compared to the averaged ensemble members with equal weights. An application demonstration using actual Sentinel-1 data and a typical test site with significant subsidence (Mexico City) completes the paper. Numéro de notice : A2015-858 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2015.09.004 Date de publication en ligne : 29/09/2015 En ligne : https://doi.org/10.1016/j.isprsjprs.2015.09.004 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79240 [article]

An advanced algorithm for deformation estimation in non-urban areas / K. Goel in ISPRS Journal of photogrammetry and remote sensing, vol 73 (September 2012)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 73 (September 2012) . - pp 100 - 110 Titre : An advanced algorithm for deformation estimation in non-urban areas Type de document : Article/Communication Auteurs : K. Goel, Auteur ; Nico Adam, Auteur Année de publication : 2012 Article en page(s) : pp 100 - 110 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] déformation de la croute terrestre [Termes IGN] filtrage du bruit [Termes IGN] image radar moirée [Termes IGN] image TanDEM-X [Termes IGN] interferométrie différentielle [Termes IGN] zone rurale Résumé : (Auteur) This paper presents an advanced differential SAR interferometry stacking algorithm for high resolution deformation monitoring in non-urban areas with a focus on distributed scatterers (DSs). Techniques such as the Small Baseline Subset Algorithm (SBAS) have been proposed for processing DSs. SBAS makes use of small baseline differential interferogram subsets. Singular value decomposition (SVD), i.e. L2 norm minimization is applied to link independent subsets separated by large baselines. However, the interferograms used in SBAS are multilooked using a rectangular window to reduce phase noise caused for instance by temporal decorrelation, resulting in a loss of resolution and the superposition of topography and deformation signals from different objects. Moreover, these have to be individually phase unwrapped and this can be especially difficult in natural terrains. An improved deformation estimation technique is presented here which exploits high resolution SAR data and is suitable for rural areas. The implemented method makes use of small baseline differential interferograms and incorporates an object adaptive spatial phase filtering and residual topography removal for an accurate phase and coherence estimation, while preserving the high resolution provided by modern satellites. This is followed by retrieval of deformation via the SBAS approach, wherein, the phase inversion is performed using an L1 norm minimization which is more robust to the typical phase unwrapping errors encountered in non-urban areas. Meter resolution TerraSAR-X data of an underground gas storage reservoir in Germany is used for demonstrating the effectiveness of this newly developed technique in rural areas. Numéro de notice : A2012-548 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2012.06.001 En ligne : https://doi.org/10.1016/j.isprsjprs.2012.06.001 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31994 [article]

Exemplaires(1)

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081-2012071	SL	Revue	Centre de documentation	Revues en salle	Disponible

A three dimensional scatterer map extends the DEM information in urban areas / Nico Adam in Revue Française de Photogrammétrie et de Télédétection, n° 182 (Juin 2006)  

Public [article]  inRevue Française de Photogrammétrie et de Télédétection > n° 182 (Juin 2006) . - pp 5 - 9 Titre : A three dimensional scatterer map extends the DEM information in urban areas Type de document : Article/Communication Auteurs : Nico Adam, Auteur ; M. Eineder, Auteur Année de publication : 2006 Conférence : ISPRS 2006, Commission 1 Symposium, From sensors to imagery 03/07/2006 06/07/2006 Champs-sur-Marne [Paris Marne-la-Vallée] France OA ISPRS Archives Article en page(s) : pp 5 - 9 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] coin réflecteur [Termes IGN] données polarimétriques [Termes IGN] image radar moirée [Termes IGN] image SRTM [Termes IGN] interféromètrie par radar à antenne synthétique [Termes IGN] MNS SRTM [Termes IGN] modèle 3D de l'espace urbain [Termes IGN] modèle numérique de surface [Termes IGN] Munich [Termes IGN] précision millimétrique [Termes IGN] tomographie [Termes IGN] zone urbaine Résumé : (Auteur) The generation of digital elevation models (DEMs) by space-born InSAR is a well-established remote sensing technique. Several application projects as for instance the shuttle radar topography mission (SRTM) have proven the outstanding capability to map the Earth's surface globally with great accuracy and constant resolution applying this technique. The short mission time of only eleven days guaranteed the homogenous quality of the generated DEM. The typical InSAR-DEM provides a snapshot of the terrain elevation at the time of acquisition including the vegetation cover. A limitation is that the Earth's cover is mapped only down to a mean radar penetration depth. Polarimetry can be applied to separate volume scattering from the double bounce effect on the ground in forested areas. But in urban areas this scattering model can not be applied. This is in contrast to the great interest in urban areas caused by the high population density and change. Nowadays, the permanent scatterer interferometry which has been invented at POLIMI is working operational and can provide supplementing information. It allows a monitoring of urban areas over time spans of more than ten years. E.g. the subsidence in such spots can be detected and monitored with millimetre accuracy. The separation of the orbit, atmosphere and topography phase effects form the basis for the extreme accuracy regarding the displacement measurement. Furthermore, the PS estimation results in a high precision DEM update at the PS position. The structure of the cities and the radar observation geometry are the reason that this simple elevation concept needs to be extended. It is very likely that more than one dominant scatterer is inside a resolution cell. Tomography can resolve this ambiguity and provides the reflectivity along cross slant range height. Consequently, a real but irregular sampled 3D map of the persistent radar scatterers can be generated which describes the city better. The dominant radar scatterers are related to buildings and other men made features. This is the reason the exact three-dimensional locations of the scatterers provide a lot of useful information on the area and the shape of the city and allowing various applications. Such a 3D map can be a better DEM input for each PS processing that allows an effective PS detection and optimal parameter estimation. A new parametric method for the detection and relative estimation of the two dominant scatterers configuration inside of a resolution cell has been developed. The developed method is more robust because it uses amplitude data only and complements the full tomography which includes the phase information. The city of Munich is one of DLR's testsite for the PS processing and the developed tomography algorithms. Examples for the generated data set and applications will be shown. The permanent scatterers are assessed in situ and the 3D position of the scatterers is checked and compared to the estimates. Copyright SFPT Numéro de notice : A2006-617 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : sans En ligne : https://www.isprs.org/proceedings/XXXVI/part1/Papers/T09-40.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28340 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
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