97,711 research outputs found
A novel optimization approach to forest height reconstruction from multi-baseline data
No full textThe paper deals with the problem of reconstructing the
height of forests from polarimetric/multi-baseline SAR data. The
approach consists of optimizing an objective functional defined
as the distance between the measured data and the data predicted
by the model at the actual estimate of the unknowns.
We indicate the role of global optimization on the performance of
the forest height reconstruction algorithm. As global optimizer, a
multilevel single-linkage method, which incorporates a local
optimization into the global search, is exploited, thus offering
computational efficiency and reliability. The performance of the
method are illustrated against numerically simulated data
Joshua Davis: Author of Spare Parts
No full textCitation: K-State First (2016). Joshua Davis: Author of Spare Parts [Flier]. Manhattan, Kansas: K-State First.Flyer advertising Joshua Davis's author talk at Kansas State University
Theoretical Performance Bounds on the Estimation of Forest Structure Parameters From Multibaseline SAR Data
No full textGiven their central role in the carbon budget, the SAR remote sensing of forests has become during the last two decades a “hot” research topic. A powerful way to analyze forest scattering consists in the coherent combination of multibaseline (MB) SAR data, possibly also polarimetric. For instance, SAR Tomography is a powerful technique whose natural output is the 3-D imaging in the range-azimuth-height space, thus allowing the resolution of multiple scatterers in height in the same cell. As a consequence, the extraction of a high amount of information is made possible, e.g. forest height and biomass, radar reflectivities, sub-canopy topography, soil humidity, volume extinction [1].
In the last years, many tomographic algorithms have been conceived for the estimation of forest structure parameters in both parametric and non parametric frameworks and their performance have been judged against the available in-situ measurements [2-5]. However, not so many efforts have been spent in the analytical derivation of theoretical performance bounds, despite their primary importance. In fact, such tools provide a benchmark against which it is possible to compare the performance of any estimator. Not only, but they alert to the physical impossibility of finding an estimator whose performance is lower than the bounds.
This work offers a contribution to tackle the performance bounding problem by resorting to the Cramér-Rao bound (CRB) theory. The CRB is a result of the information theory which provides a lower bound on the variance of any unbiased estimator of an unknown parameter. Given also its relative easiness of calculation, the CRB is widely used in the statistical signal processing to judge the efficiency of the parameter estimators. In the specific MB SAR field, it could also be a very useful instrument to characterize the potentials of acquisition configurations and possibly as a guideline in designing acquisition patterns (mission planning) and systems. An interesting extension of the CRB is represented by the Hybrid CRB (HCRB), in which the presence of random phase offsets between different acquisitions (e.g. due to non perfect baseline estimation and/or propagation effects through the atmosphere) can be taken into account.
In particular, in this work the CRB and HCRB derivations are focused to the analysis of forest areas by assuming a two-layer model for the MB data vector, i.e. a ground layer and a canopy layer, with different characteristics of their vertical structure. Starting from the very general formulations of MB bounds in [6] and [7], ready-to-use CRB and HCRB formulas are given for forest scenarios. Moreover, the obtained precision limits on the parameters of interest are calculated numerically for some realistic acquisition patterns and for different observed scenarios. The presence of temporal decorrelation is considered in the model, which is recognized to be one of the main application barriers of MB repeat-pass forest observations, especially from space [8].
References
[1] A. Reigber, A.Moreira, “First Demonstration of Airborne SAR Tomography Using Multibaseline L-Band Data,” IEEE Trans. on Geoscience and Remote Sensing, vol. 38, 2000.
[2] F. Lombardini, M. Pardini, “Experiments of Tomography-Based SAR Techniques with P-Band Polarimetric Data”, Proc. of the 2009 ESA PolInSAR Workshop.
[3] M. Nannini, R. Scheiber, et al., “Estimation of the Minimum Number of Tracks for SAR Tomography,” IEEE Trans. on Geoscience and Remote Sensing, vol. 47, 2009.
[4] M. Neumann, L. Ferro-Famil, et al., “Estimation of Forest Structure, Ground, and Canopy Layer Characteristics From Multibaseline Polarimetric Interferometric Data,” IEEE Trans. on Geoscience and Remote Sensing, vol. 48, 2010.
[5] S. Tebaldini, “Single and Multipolarimetric SAR Tomography of Forested Areas: A Parametric Approach,” IEEE Trans. on Geoscience and Remote Sensing, vol. 48, 2010.
[6] F. Gini, F. Lombardini, M. Montanari, “Layover Solution in Multibaseline SAR Interferometry,” IEEE Trans. on Aerospace and Electronic Systems, vol. 38, 2002.
[7] M. Pardini, F. Lombardini, F. Gini, “The Hybrid Cramér-Rao Bound for Broadside DOA Estimation of Extended Sources in Presence of Array Errors,” IEEE Trans. on Signal Processing, vol. 56, pp. 1726–1730, Apr 2008.
[8] F. Lombardini, F. Cai, M. Pardini, “Parametric Differential SAR Tomography of decorrelating Volume Scatterers,” Proc. of the 2009 European Radar Conference (EURAD)
Coherent scatterers detection in glacier environments by means of TerraSAR-X images
No full textThis paper investigates the detection of Coherent Scatterers (CSs) in Ice and Glacier terrain by means of Ter-raSAR-X images in the test case of the Helheim Glacier in Greenland. CSs are evaluated with respect to detec-tion, properties and potential applications. The detection of CSs by means of TerraSAR-X data is discussed and optimised detection schemata for minimising false alarm rate are investigated. Properties and quality of the de-tected CSs are analysed
Steven Johnson Author Talk Poster
No full textK-State Book NetworkA poster advertising an author talk by Steven Johnson at Kansas State University on September 3, 2014. Steven Johnson's book "The Ghost Map" was the 2014-2015 common book
Coherent scatterers detection: application over glacier terrain using TerraSAR-X time series data
No full textThis paper investigates the detection of Coherent Scatterers
(CSs) in ice and glacier terrain by means of TerraSAR-X
time series data in the test site of the Helheim Glacier in
Greenland. CSs are evaluated with respect to detection and
potential applications. Applying optimized detection scheme
can be useful for retrieving information about the glacier
movement using time series data. Finally, some conclusions
about the temporal stability of natural CSs are obtained by
analyzing the rocky area around the glacier
Analysis of forest-slab height inversion from multibaseline SAR data
No full textWe address the problem of reconstructing parameters
regarding the vertical structure of forests from multibaseline
SAR data. The attention is focused on the retrieval of the
forest height so that the case of vanishing ground scattering is
considered.
The cross-spectral density of the scattered field is taken as datum
of the problem and the forest height is searched for by tackling
an optimization problem. An analytical and numerical analysis
of the involved functional is performed by taking due care to the
discrete nature of the scatterers
On the Performance of Forest Vertical Structure Estimation via Polarization Coherence Tomography
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