Mark L. Williams

Overview of the PolSARpro V4.0 software. the open source toolbox for polarimetric and interferometric polarimetric SAR data processing

The objective of this paper is to make a review of the current status of the PolSARpro v4.0 Software (Polarimetric SAR Data Processing and Educational Toolbox), developed under contract to ESA by a consortium comprising I.E.T.R at the University of Rennes 1, AELc, DLR-HR and Dr mark Williams from Adelaide. The objective of this current project is to provide Educational Software that offers a tool for self-education in the field of Polarimetric SAR data analysis at University level and a comprehensive suite of functions for the scientific exploitation of fully and partially polarimetric multi-data sets and the development of applications for such data. The PolSARpro v4.0 Software establishes a foundation for the exploitation of Polarimetric techniques for scientific developments and stimulates research and applications developments using PolSAR and PolInSAR data.

Enhanced Simulation of Radar Backscatter From Forests Using LiDAR and Optical Data

Focusing on a forest dominated by Poplar Box (Eucalyptus populnea) near Injune in Queensland, Australia, light detection and ranging (LiDAR) and optical remote sensing data are integrated with tree- and stand-level information to parameterize a coherent L-band synthetic aperture radar (SAR) imaging simulation that models microwave penetration and interaction with the canopy, understory, and ground. The approach used LiDAR data to generate a three-dimensional representation of the distribution of tree components (leaves and small branches) by species (based on 1-m3 voxels) and the ground surface. Tree trunks were mapped across a 7.5-ha forest stand using a LiDAR-derived height-scaled crown openness index. Primary and secondary branches were modeled as tapering cylinders and linked the canopy voxels to the LiDAR trunks. The dimensions of vegetation and soil components and their geometric and dielectric properties required by the model were calibrated with field-based measurements. Visual and numerical comparison between NASA JPL Airborne SAR data and the model simulation suggests the effective modeling of SAR imagery at L-band. The study provides a proof-of-concept approach for integrating LiDAR data in the parameterization of coherent SAR simulation models, and the model presents options for better understanding of the information content of SAR data in real forest situations

Potential for Surface Parameter Estimation Using Compact Polarimetric SAR

The retrieval of soil surface parameters using a dual-polarization synthetic aperture radar operating in a compact polarimetric mode is examined. It is shown that by employing a two-component model of surface polarimetric coherency, soil surface parameter retrieval is possible directly from measurements without the need for any additional assumptions. Model surface parameters inverted by using the full polarimetric coherency matrix may be recovered equally well from a compact polarimetric coherency matrix.

Analysis of geosar dual-band InSAR data for peruvian forest

At present there is no consensus as to which remote sensing technologies are appropriate for tropical forest biomass estimation. Cloud cover in the tropics and biomass saturation suggest that a combination of low-frequency SAR and interferometry (either PolInSAR or dual-band interferometric SAR - DBInSAR) could provide a solution.

The negative alpha filter: a new Processing technique for polarimetric SAR interferometry

In this letter we develop a new concept, the negative alpha filter, which we suggest has application for quantitative estimation of surface parameters beneath vegetation using polarimetric synthetic aperture radar (SAR) interferometry (POLInSAR). We first derive the filter and then validate it using simulations of L-band coherent forest scattering. We then show initial results of applying the filter to airborne data from the German Aerospace Centers E-SAR L-band sensor.

Predictions of SAR polarimetry and InSAR coherence for a model wheat canopy

We investigate the potential for biophysical parameter retrieval using polarimetric, interferometric Synthetic Aperture Radar (SAR) by applying a coherent simulation technique to crop-like vegetation. The crop coherent SAR simulation calculates scattered returns from plant elements using a mean field approximation. The scattered fields from small sections of each of these plant elements are focused in the simulated SAR image according to the SAR imaging geometry, and the nature of the scattering interaction. The model is fully coherent and permits the investigation of the coherence properties of a vegetation canopy as a function of SAR imaging and canopy parameters. We have applied the model to a simulated canopy of model wheat plants described by parameters based on measurements reported in the literature. The polarimetric and coherence properties of simulated imagery are examined and discussed with reference to current knowledge and expectation.

The role of LiDAR data in understanding the relation between forest structure and SAR imagery

As part of the 2000 PACRIM II Mission to Australia, polarimetric Synthetic Aperture Radar (SAR) data were acquired near Injune, central Queensland, Australia. The primary purpose of the acquisition was to better understand the role of SAR for retrieving biophysical properties of native forests through either empirical relationships or simulation modeling. In this paper, we outline the generation of a three-dimensional representation of the forest structure and component elements (leaves, branches and trunks) using field, airborne LiDAR and CASI data and aerial photography acquired at the same time as the AIRSAR. We then show how this representation formed the basis of the input to a coherent SAR imaging simulation that models microwave penetration and interaction with canopy and understorey components. A preliminary comparison between actual AIRSAR and simulated SAR data for a poplar box (Eucalyptus populnea) woodland suggests effective modelling of SAR backscatter.

Corner reflectors for the Australian Geophysical Observing System and support for calibration of satellite-borne synthetic aperture radars

Geoscience Australia is implementing the geospatial component of the Australian Geophysical Observing System (AGOS). AGOS infrastructure will include a network of radar corner reflectors, in addition to a geodetic ground mark network for monitoring ground deformation in Australia. In this paper we describe the design of radar corner reflectors for deformation studies and calibration of Synthetic Aperture Radar (SAR) sensors. Through a prototyping campaign in 2013 we will seek a single reflector design that can be used for deformation and calibration studies using X- and C-band SAR sensors. Prototyping will involve precise determination of reflector radar cross section at an outdoor radar test range and a temporary field deployment in the Canberra region during which X- and C-band data acquisitions will be made from orbiting SAR satellites. We also outline plans to deploy corner reflectors in the Surat Basin of Queensland to monitor ground deformation induced by coal seam gas (CSG) extraction.

Dependence of P-band interferometric height on forest parameters from simulation and observation

GeoSAR is a unique dual-band, interferometric SAR (DBInSAR) sensor capable of collecting single-pass, X-band (VV) and P-band (HH) interferometric data simultaneously. In this paper we examine the dependence of the P-band HH interferometric phase centre height upon forest and terrain parameters. We develop a simple model for P-band GeoSAR observations, and use the model to show how the elevation in P-band HH phase centre height above true ground height is related to the volume-to-ground scattering ratio. GeoSAR is not fully-polarimetric, but records cross-polar (HV) returns at P-band (although not interferometrically). We conjecture that these returns are dominated by direct-volume scattering and related to the direct-volume HH backscatter. We use this relationship to model the dependence of the P-band HH DTM height upon the HV/HH ratio, and the difference in X-band DEM with P-band DTM heights. The relationships are examined using simulated forest InSAR data, and a model is proposed for ground-height and tree-height estimation using DBInSAR that does not require full polarimetry.

Interoperability of multi-frequency SAR data for forest information extraction in support of national MRV systems

Continuity of earth observation data is paramount to operational forest information monitoring in support of national accountability of forest and carbon stocks. Following the loss of ALOS PALSAR in May 2011, the minimum 2 year gap before PALSAR-2 comes online, and the superiority of L-band data for forest monitoring, this paper addresses the issue of interoperability of SAR data through comparison of forest/non-forest, land cover and deforestation derived from independent and combined classifications of PALSAR and RADARSAT-2 data. Forest/non-forest mapping accuracies were highest using PALSAR data alone. The combined use of C- and L-band data resulted in higher forest/non-forest mapping accuracies compared to using C-band data alone. Attributed largely to an increased capacity for penetration of the vegetation canopy and interaction with woody structures, L-band SAR is most suited to forest cover mapping. Without a dense time-series, the separation of cleared or deforested land and regrowth areas is more difficult using C-band alone.