139 research outputs found
SAR interferometric phase statistics in wavelet domain
Synthetic aperture radar (SAR) interferometry is employed to obtain
topographic information. Owing to noise, interferometric information
has to be filtered. The wavelet transform can be employed to filter the
interferometric phase, maintaining the spatial resolution, but new
signal models have to be studied in this domain for further processing
Polarimetric SAR Speckle Noise Model
Synthetic aperture radar (SAR) data are affected by speckle noise, originated by the SAR system's coherent nature. The problem of speckle noise in one-dimensional (1-D) data is already solved, as speckle has a multiplicative characteristic. SAR polarimetry represents an extension to multidimensional data by the use of polarization wave diversity. As a consequence of the existence of a correlation degree between the SAR images, the 1-D speckle noise model cannot be extended to multidimensional SAR data. This paper is devoted to present a completely new speckle noise model for the complex covariance matrix describing polarimetric SAR data in the distributed scatterers case. As is shown, this new model is able to identify which are the noise mechanisms in all the covariance matrix elements. The speckle noise model is validated by using real L-band polarimetric data acquired with the German E-SAR sensor.Synthetic aperture radar (SAR) data are affected by
speckle noise, originated by the SAR system’s coherent nature.
The problem of speckle noise in one-dimensional (1-D) data is
already solved, as speckle has a multiplicative characteristic. SAR
polarimetry represents an extension to multidimensional data by
the use of polarization wave diversity. As a consequence of the
existence of a correlation degree between the SAR images, the
1-D speckle noise model cannot be extended to multidimensional
SAR data. This paper is devoted to present a completely new
speckle noise model for the complex covariance matrix describing
polarimetric SAR data in the distributed scatterers case. As will
be shown, this new model is able to identify which are the noise
mechanisms in all the covariance matrix elements. The speckle
noise model is validated by using real L-band polarimetric data
acquired with the German E-SAR sensor
Wavelet Transform-Based Interferometric SAR Coherence Estimator
A novel method to estimate interferometric coherence in synthetic aperture radar interferometry is proposed. It is demonstrated that this approach is not affected by the terrain topography, contrary to multilook techniques. In addition, since the method is based on the two-dimensional discrete wavelet packet transform, it allows recovering coherence information with a high spatial resolution. Results derived from simulated and experimental ESAR-DLR X- and L-band interferograms corroborate the performance of the proposed technique.Peer Reviewe
PolSAR and PolInSAR model based information estimation
Speckle for multidimensional SAR data may be modeled as the combination of multiplicative and additive noise sources.
As demonstrated, the use of this noise model does not corrupt the estimation of physical information from PolInSAR data. The definition of a model based PolInSAR filter allows also the computation of relative errors for estimated heights of forested areas from PolInSAR data.Peer ReviewedPostprint (published version
Multidimensional speckle noise model
One of the main problems of SAR imagery is the presence of speckle noise, originated by the inherent coherent nature of this type of systems. For one-dimensional SAR systems it has been demonstrated that speckle can be considered as a multiplicative noise term. Nevertheless, this simple model cannot be exported when multidimensional SAR imagery is addressed. This paper is devoted to present the latest advances into the definition of a multidimensional speckle noise model which does not depend on the data dimensionality. Speckle noise may be modeled by multiplicative and additive noise sources, whose combination is determined by the data's correlation structure. The validity of the proposed model is demonstrated by its application to a real L-band multidimensional SAR dataset acquired by the German ESAR sensor
Actividades del grupo EEF en el contexto de la red europea TMR "Polarimetría radar: Teoría y aplicaciones"
The activity of the EEF group in the TMR European Project Radar Polarimetry: Theory and Applications will be presented in this paper. We have developed new polarimetric-interferometric retrieval algorithms and enhancement techniques. These methods will be showed briefly in the next points.Peer ReviewedPostprint (published version
Ground topography estimation on over forests considering polarimetric SAR interferometry
The work detailed in this paper analyzes the topographic phase retrieval process on forested areas by means of Polarimetric
Interferometric SAR data. On the basis of the Random Volume over Ground scattering model, an alternative implementation for the retrieval of the topographic phase, avoiding
the bias introduced by the volumetric scattering components is presented.Peer ReviewedPostprint (published version
Impact of wind-induced scatterers motion on GB-SAR imaging
© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Ground-based synthetic aperture radar (GB-SAR) sensors represent a cost-effective solution for change detection and ground displacement assessment of small-scale areas in real-time early warning applications. GB-SAR systems based on stepped linear frequency modulated continuous wave signals have led to several improvements such as a significant reduction of the acquisition time. Nevertheless, the acquisition time is still long enough to force a degradation of the quality of the reconstructed images because of possible short-term variable reflectivity of the scenario. This reduction of the quality may degrade the differential interferometric detection process. In scenarios where interesting targets are surrounded by vegetation, this is normally related to atmospheric conditions, in particular, the wind. The present paper characterizes the effect of the short-term variable reflectivity in the GB-SAR image reconstruction and evaluates its equivalent blurring effect, the decorrelation introduced in the SAR images, and the degradation of the extracted parameters. In order to validate the results, the study assesses different GB-SAR images obtained with the RISKSAR-X sensor, which has been developed by the Universitat Politècnica de Catalunya.Peer ReviewedPostprint (published version
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Postprint (author’s final draft
Evolution of protoplanetary disks from their taxonomy in scattered light: Group I vs. Group II
High-resolution imaging reveals a large morphological variety of
protoplanetary disks. To date, no constraints on their global evolution have
been found from this census. An evolutionary classification of disks was
proposed based on their IR spectral energy distribution, with the Group I
sources showing a prominent cold component ascribed to an earlier stage of
evolution than Group II. Disk evolution can be constrained from the comparison
of disks with different properties. A first attempt of disk taxonomy is now
possible thanks to the increasing number of high-resolution images of Herbig
Ae/Be stars becoming available. Near-IR images of six Group II disks in
scattered light were obtained with VLT/NACO in Polarimetric Differential
Imaging, which is the most efficient technique to image the light scattered by
the disk material close to the stars. We compare the stellar/disk properties of
this sample with those of well-studied Group I sources available from the
literature. Three Group II disks are detected. The brightness distribution in
the disk of HD163296 indicates the presence of a persistent ring-like structure
with a possible connection with the CO snowline. A rather compact (less than
100 AU) disk is detected around HD142666 and AK Sco. A taxonomic analysis of 17
Herbig Ae/Be sources reveals that the difference between Group I and Group II
is due to the presence or absence of a large disk cavity (larger than 5 AU).
There is no evidence supporting the evolution from Group I to Group II. Group
II are not evolved version of the Group I. Within the Group II disks, very
different geometries (both self-shadowed and compact) exist. HD163296 could be
the primordial version of a typical Group I. Other Group II, like AK Sco and
HD142666, could be smaller counterpart of Group I unable to open cavities as
large as those of Group I.Comment: 16 pages, 7 figures, published by A&
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