151 research outputs found
Polarimetric Scattering Model for Methane Bubbles Trapped in the Ice of Sub-Artic Lakes
No full textIn this work we propose a model for the polarimetric backscattering of shallow sub-arctic lakes, which are frozen usually up to two meters depth during winter. The model takes into account the inhomogeneities in the ice layer introduced mainly by CH4 bubbles trapped in the lake ice. The model is validated against experimental data acquired by ALOS-PalSAR
Vertical Resolution Enhancement by Applying Polarimetric Spectral Analysis Techniques to Multibaseline InSAR Data
No full textPolarimetric spectral analysis techniques have been recently
introduced for processing multibaseline interferometric
synthetic aperture radar data that are affected by the
speckle phenomenon. In this paper, their phase estimation
accuracy for retrieving the three-dimensional structure of
scatterers from measurements corrupted by multiplicative
noise is examined. The performance of the polarimetric
beamforming, Capon, and MUSIC algorithms is investigated
by Monte Carlo simulations and compared with the polarimetric Cramer-Rao bound. It is demonstrated by the CRLB that radar probing systems possessing polarization diversity offer the potential of considerably improving the information extracted from the observation space enlarged by scattering polarimetry. Moreover, it is shown that the polarimetric algorithms lead to noticeably enhanced estimation precision, in particular in terms of refined resolution, under the condition of polarization diversity
Boreal forest biomass classification with TanDEM-X
No full textHigh spatial resolution X-band interferometric SAR data from the TanDEM-X, in the operational DEM generation mode, are sensitive to forest structure and can therefore be used for thematic boreal forest classification of forest environments. The interferometric coherence in absence of temporal decorrelation depends strongly on forest height and structure. Due to the rather homogenous structure of boreal forest, forest biomass can be derived from forest height, on the basis of allometric equations with sufficient accuracy to be used for thematic classification applications. Two test sites in mid- and southern Sweden are investigated. A maximum of 4 biomass classes, up to 250 Mg/ha, are achieved. Larger spatial baselines result in better classification performances
Potential of TanDEM-X for forest parameter estimation
No full textIt was demonstrated that interferometric volume coherence is sensitive to vertical forest structure. This is true even for high frequencies as X-band. Resent Experiments demonstrated the potential of X-band to estimate key forest parameters like forest height. The main limitations at X-band are the high extinction values (up to 1dB/m and larger) for forests and the high sensitivity of X-band to temporal decorrelation. With the launch of the Tan-DEM-X satellite, for the first time single pass interferometric X-band data from a space borne system become available. In this paper the potential of X-band for forest height inversion is discussed and experimental results from different relevant campaigns are introduced and discussed
Long-wavelength Pol-InSAR for glacier ice extinction estimation
No full textIn recent years there has been increased interest in using synthetic aperture radar (SAR) to study and monitor glaciers for climate change research. This paper describes the estimation of ice extinctions through modelling of Pol-InSAR (polarimetric interferometric SAR) coherences as a combination of a surface contribution (from the snow-firn interface and wind-induced features) and a volume response. Ground-to-volume scattering ratios derived from a novel polarimetric decomposition are used in conjunction with Pol-InSAR interferometric coherence magnitudes to invert the extinction of the ice layer. The inversion is performed with experimental airborne Pol-InSAR data at L- and P-band collected using DLR's E-SAR system over the Austfonna ice cap in Svalbard, Norway as part of the 2007 ICESAR campaign. Extinction-dependencies on frequency and glacier zone are investigated, and validation is performed comparing P-band sounder data to inverted extinction values
Very-High-Resolution Airborne Synthetic Aperture Radar Imaging: Signal Processing and Applications
No full textOrientation Angle Estimation Over Forested Terrain Using P-band POLSAR Data
No full textOne important secondary objective of the proposed Earth-
Explorer Candidate Mission BIOMASS is the retrieval of
a digital terrain model (DTM) using satellite-borne P-band
SAR data. The interferometric phase acquired in repeat-pass
mode may be affected by ionospheric effects leading to corrupted phase estimates and, consequently, to errors in the
derived DTM. In contrast, line-of-sight orientation angles
induced by azimuth slopes can be estimated using single-pass
POLSAR measurements. The orientation angle estimates
allow a necessary pre-processing of POLSAR observations
and the retrieval of topographic information such as a DTM.
In this study, the performance of the circular polarization
method for orientation angle estimation is examined over
forested areas. To this end, the orientation angles computed
from P-band POLSAR data are compared with the results
obtained from LIDAR DTMs. In particular, the estimation
performance is investigated with respect to the impact of topography and vegetation. POLSAR data at P-band are used
that have been acquired by the E-SAR system of DLR over
three forested test sites: two boreal forests in Sweden (one
over flat terrain located at Remningstorp, the other over terrain with topographic variations at Krycklan) and the tropical forest Mawas in Indonesia over flat terrain
Potential & challenges of polarimetric SAR interferometry techniques for forest parameter estimation in the context of the BIOMASS mission
No full textWorld forests contain a significant amount of carbon that is, in consequence of natural and human induced
deforestation and regrowth processes, affected by rapid changes and therefore difficult to quantify in terms of biomass/carbon storage. This uncertainty remains because of the lack of reliable and frequent information of biomass levels on a global scale. Spaceborne Synthetic Aperture Radar (SAR) could provide the required global and temporal coverage of the world’s forested areas. Innovative new inversion approaches allow today accurate meassurement of vegetation structure arameters such as forest height and biomass. The coherent combination of polarimetric and interferometric SAR at lower frequencies by means of Pol-InSAR is sensitive to the vertical distribution of scattering processes within a resolution cell and can be used for model-based inversion of forest height and structural parameters
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