Radar-Coding and Geocoding Lookup Tables for the Fusion of GIS Data and SAR images in Mountain Areas

International audienceSynthetic aperture radar (SAR) image orthorectification induces an important alteration of information due to the side-looking geometry of SAR acquisition. In high-relief areas, the difficulty is increased by the foldover effect: The images acquired with low incidence angles cannot be registered by a bijective transformation like polynomial transformations, as usually proposed by conventional software. In this letter, a simple and efficient method, fitted to geocoded data and SAR images, is introduced to propose a generic coregistration tool that takes SAR geometry into account without requiring the exact sensor model, specific parameters, and precise navigation data. This method is based on a simulated SAR image and on the computation of lookup tables (LUTs) that represent the coordinate transform from one geometry to the other. Results are presented on a high-relief area in the Alps, where satellite and airborne SAR images are used for glacier evolution monitoring. A comparison to other sensor-independent approaches has been performed, showing that the proposed approach performs better in mountain areas. The resulting LUTs allow merging SAR data with the georeferenced data, either in ground geometry by orthorectifying the SAR information or in radar geometry by the inverse transformation, namely, radar-coding data from a geographic information system, to improve the analysis of SAR images and the result interpretation

Monitoring Alpine Glaciers with ALOS SAR and Optical data

International audienceThe monitoring of temperate glacier activity is one of the applications which require the combined use of optical and SAR data. It should become feasible thanks to the ALOS PRISM and PALSAR sensors. In this paper, we present the interest of using L-band polarimetric interferometric SAR data and high resolution panchromatic stereoscopic data to monitor moving temperate glaciers made of ice, snow and rocks. The scientific issues are described and a test-site located in the Mont-Blanc region in the Alps is proposed for specific experiment and validation. The Mont-Blanc test-site includes two well-known glaciers (Mer-de-Glace and Argentière glaciers) where a large data set has been collected: ERS, RADARSAT and ENVISAT data, airborne E-SAR data (X, C, L and P bands), airborne photographs, GPS and GPR in-situ measurements..

Coherent-stable scatterers detection in SAR multi-interferograms: feature fuzzy fusion in Alpine glacier geophysical context

International audienceSAR interferometry (InSAR) performs two acquisitions (spatially separated by the baseline) of the signal back-scattered by the resolution cell which contains height and/or displacement information. Repeat pass spaceborne interferometry provides multi-interferograms which can be used to extract such information either by combining the multi-temporal results of conventional interferometry or by a different approach based on specific targets: the coherent stable scatterers (CSS). In this paper a two-step approach is proposed to obtain specific features from multi-temporal InSAR data sets. The first step consists in extracting image attributes related to the useful information. The second step consists in merging the attributes using an interactive fuzzy fusion technique. The interactive fuzzy fusion is proposed to provide end-users with a simple and easily understandable tool for tuning the detection results. The method is applied on a data set of five co-registered ERS 1/2 tandems from the French Alps (the Mont-Blanc region), including two temperate glaciers: the Argenti'ere and the Mer-de-glace. The results illustrate how the end-user can combine the proposed attributes to detect the presence of CSS or distributed stable scatterers usefull for multi-temporal analysis

Radar Rectification of GIS Data for SAR Image Analysis in Mountain Areas

4 pages , document Pdf dans CD-ROM http://www.vde-verlag.de/data/buecher.php?action=bookdetail&vertriebsnr=453084&loc=deInternational audienceGeographic Information System, GIS, are dedicated to view and to process georeferenced images. For the data fusion of Synthetic Aperture Radar (SAR) images with other information sources, one usually uses processing software to orthorectify the SAR images in order to add them in a GIS. Nevertheless, this projection involves an important alteration of the information of SAR images. In this paper, we propose a simple and efficient method by inverting the process: the radar rectification of georeferenced data. Coding data from a GIS into the radar geometry, allows the use of different information sources to improve the analysis of SAR images and the result interpretation. This approach is applied to a high relief area in the Alps, where SAR images are used for glacier evolution monitoring. Results are illustrated over the Chamonix Mont-Blanc test site on spaceborne images (ERS and ENVISAT data) and airborne E-SAR images

Radar rectification of georeferenced information for data analysis in high mountain areas

National audienceGeographic Information System, GIS, are very useful in order to view and to process georeferenced images. For the data fusion of Synthetic Aperture Radar images, SAR, with other information sources, one usually uses interferometric processing software to orthorectify the SAR images in order to add them in a GIS. Nevertheless, this projection involves an important alteration of the information of SAR images. In this paper, we propose a simple and efficient method by inverting the process : the radar-rectification of georeferenced data. By coding data from a GIS into the radar geometry , we can use different information sources to improve the analysis of SAR images and the results interpretation. We apply this method on a high relief area in the region of the Mont-Blanc, where SAR images are useful to survey the glacier evolution

Interactive learning of implicative fuzzy rules applied to the classification of POLSAR features in the context of Alpine glaciers

With the developments of airborne, and recently spaceborne, fully polarimetric synthetic aperture radar (POL-SAR) sensors, microwave remote sensing offers new opportunity to observe and understand geophysical phenomena. However, extracting information from the multi-component complex POLSAR images requires several processing stages, including the POLSAR feature estimation to reveal different backscattering mechanisms, and the fusion of these features to help the end-user to perform detection or classification tasks. In this paper, a new data fusion method based on interactive learning of implicative fuzzy rules is presented. It allows to perform supervised classification by analyzing the training set clusters in the different 2D feature spaces resulting from the different attribute pairs. Experimental results are presented on a real POLSAR data set acquired by the airborne E-SAR system over temperate glaciers in the Alps. They illustrate the interest of the proposed fusion approach for POLSAR data analysis and the potential of the POLSAR imagery for the monitoring of temperate glacier evolution.

Rectification radar de données géoréférencées : application à l'analyse de données dans les régions de haute montagne

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Simulation of SAR Images and Radar Coding of Georeferenced Information for Temperate Glacier Monitoring,

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Multi-date ERS tandem interferogram analysis: application to alpine glaciers

International audienceTemperate glaciers are an indicator of the local effects of global climate change. For economical and security reasons in the surrounding areas, the monitoring of those geophysical objects is being a necessity. SAR data are expected to provide dense measurements of physical parameters which are necessary to detect significant changes and to constrain glacier flow models. In this paper, five descending one-day ERS- 1/2 tandem interferometric data pairs from July 1995 to April 1996 are studied in the Chamonix Mont-Blanc area (French Alps). This multi-temporal interferogram series is used to analyse the coherence levels and fringe patterns over nine glaciers. Moreover, when the coherence is sufficient, Differential SAR Interferometry (D-InSAR) processing are applicable to derive a three-dimensional (3-D) velocity fields. An expert knowledge and a ten years measurements analysis of glacier flow are used to fix the line of sight (LOS) displacement offset. Finally, an analysis of the wrapped phase difference between interferograms is exposed to detect the presence of residual topographic fringes and to characterize the surface flow field evolution

High-Resolution SAR Interferometry: Estimation of Local Frequencies in the Context of Alpine Glaciers

Synthetic aperture radar (SAR) interferometric data offer the opportunity to measure temperate glacier surface topography and displacement. The increase of the resolution provided by the most recent SAR systems has some critical implications. For instance, a reliable estimate of the phase gradient can only be achieved by using interferogram local frequencies. In this paper, an original two-step method for estimating local frequencies is proposed. The 2-D phase signal is considered to have two deterministic components corresponding to low-resolution (LR) fringes and high-resolution (HR) patterns due to the local microrelief, respectively. The first step of the proposed algorithm consists in the LR phase flattening. In the second step, the local HR frequencies are estimated from the phase 2-D autocorrelation function computed on adaptive neighborhoods. This neighborhood is the set of connected pixels belonging to the same HR spatial feature and respecting the “local stationarity” hypothesis. Results with bothsimulated TerraSAR-X interferograms and real airborne E-SAR images are presented to illustrate the potential of the proposed method