On the extension of multidimensional speckle noise model from single-look to multilook SAR imagery

Speckle noise represents one of the major problems when synthetic aperture radar (SAR) data are considered. Despite the fact that speckle is caused by the scattering process itself, it must be considered as a noise source due to the complexity of the scattering process. The presence of speckle makes data interpretation difficult, but it also affects the quantitative retrieval of physical parameters. In the case of one-dimensional SAR systems, speckle is completely determined by a multiplicative noise component. Nevertheless, for multidimensional SAR systems, speckle results from the combination of multiplicative and additive noise components. This model has been first developed for single-look data. The objective of this paper is to extend the single-look data model to define a multilook multidimensional speckle noise model. The asymptotic analysis of this extension, for a large number of averaged samples, is also considered to assess the model properties. Details and validation of the multilook multidimensional speckle noise model are provided both theoretically and by means of experimental SAR data acquired by the experimental synthetic aperture radar system, operated by the German Aerospace Center.Peer Reviewe

Coherence estimation in synthetic aperture radar data based on speckle noise modeling

In the past we proposed a multidimensional speckle noise model to which we now include systematic phase variation effects. This extension makes it possible to define what is believed to be a novel coherence model able to identify the different sources of bias when coherence is estimated on multidimensional synthetic radar aperture (SAR) data. On the one hand, low coherence biases are basically due to the complex additive speckle noise component of the Hermitian product of two SAR images. On the other hand, the availability of the coherence model permits us to quantify the bias due to topography when multilook filtering is considered, permitting us to establish the conditions upon which information may be estimated independently of topography. Based on the coherence model, two coherence estimation approaches, aiming to reduce the different biases, are proposed. Results with simulated and experimental polarimetric and interferometric SAR data illustrate and validate both, the coherence model and the coherence estimation algorithms.Peer Reviewe

Matching stereoscopic SAR images for radargrammetric applications

International audienceThe aim of this paper is to present our studies about extraction of 3D information from radar images. Several radargrammetric methods allow DEM (Digital Elevation Model) generation from SAR images and we take a special interest to stereoscopic method. The main idea is to match image stereo pairs, to create a disparity map from one image to the other and to compute elevation thanks to the incidences angle

Radargrammetric SAR Image Processing

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SCATTERING MECHANISM ANALYSIS USING MULTI-ANGULAR POLARIMETRIC RADARSAT-2 DATASETS

International audienceThe objective of this study is to analyze scattering mecha- nisms using multi-incidence angle observations over agri- cultural fields. Radarsat-2 datasets acquired in the end of March / beginning of April with four different ranges of incidence angle are explored using polarimetric decom- position methodology. The results show that single scat- tering is always the dominant scattering mechanism over test sites, although single scattering occurs on bare sur- face is significantly stronger than that occurs in vegeta- tion canopy. As incidence angle increases, single scatter- ing decreases, and volumetric scattering increase as ex- pected. Therefore, lower incidence angle acquisition is appropriate to characterize soil moisture over bare sur- face due to the limited effect of roughness, while higher incidence angle is suitable for surface roughness iden- tification over bare surface and plant height description over vegetation canopy. Nevertheless, as the incidence angle increases towards 4

SOIL MOISTURE CHARACTERIZATION USING MULTI-ANGULAR POLARIMETRIC RADARSAT-2 DATASETS

International audienceThe use of multi-angular polarimetric datasets instead of the standard single-angular data is considered to be a solution to improve the effectiveness of bare soil char- acterization. However, the potential of polarimetric pa- rameters derived from the multi-angular SAR datasets was studied little, particularly for the C band polarimet- ric datasets. In this study, the sensitivity of polarimetric descriptors from single and multiple incidence angle acquisitions is investigated against in situ soil moisture and surface roughness. The behaviours of polarimetric descriptors are compared with the simulations using integral equation model (IEM). The results show that the variation of polarimetric descriptors in term of soil moisture as well as surface roughness is in accordance with the IEM simulations; even though the variation scale is different between the real data and simulation (The simulation is more sensitive than the real data). The polarimetric sensitivity found in this study provides additional evidences for the potential utilization of multi-angular polarimetric SAR datasets for bare sur- face characterization

Statistical assessment of eigenvector-based target decomposition theorems in radar polarimetry

© 2005 IEEE.Carlos López-Martínez, Eric Pottier and Shane R. Cloud

Investigations on OFDM Signal for Range Ambiguity Suppression in SAR Configuration

International audienceThis paper presents an opportunity to cancel range ambiguities in synthetic aperture radar (SAR) configuration. One of the limitations of SAR systems is the range ambiguity phenomenon that appears with long delayed echoes. The reflected signal corresponding to one pulse is detected when the radar has already transmitted the next pulse. Thus, this signal is considered as an echo from the next pulse. This paper investigates the opportunity of coding the transmitted pulses using an orthogonal frequency-division multiplexing pulse. The results show that coded-OFDM signals outperform conventional chirp signal and make it possible to relax constraints placed upon the pulse repetition frequency