Seminar Series No. 8: Applications in Microwave Remote Sensing

Dr Mark Williams

Date: 2008-06-17
Time: 14:00 to 15:00
Venue: Tutorial room 6202, Building 6, Level 2


Current developments in microwave remote sensing include increasingly sophisticated applications in biophysical parameter retrieval. The newest techniques exploit the use of polarimetry and interferometry, both in isolation and in combination, particularly for soil moisture recovery and forest parameter estimation. The most recent advances call for the best synthetic aperture radar (SAR) technology: with full polarimetry, high bandwidth, and tight control over platform motion providing precise repeat-pass capability. Much of the work in forest parameter retrieval has been aided by the development and exploitation of physics-based simulations. Given sufficient fidelity, validated simulations provide a means of testing remote sensing algorithms, using accurate ground data: the acquisition of which is a most problematic and costly activity. The presentation will describe briefly one such simulation model, how it has been employed to demonstrate several advanced concepts, and its current use in radar remote sensing research. The most advanced, fully polarimetric SAR systems, transmitting and receiving on two orthogonal polarizations, are capable of measuring the complete scattering matrix needed to characterise and classify natural terrain. Dual polarization SAR systems, transmitting only a single polarization, and receiving on two orthogonal polarizations, offer several advantages over their more proficient cousins. However they have the disadvantage of collecting only reduced polarimetric scattering information. Nevertheless there are instances where full polarimetric information is not necessary, and where it is possible to recover desired information using an alternative set of measurements. Two such instances will be discussed. The first is a recent result which demonstrates how soil moisture may be recovered using compact polarimetric SAR operating in a number of different modes, with performance commensurate with fully-polarimetric soil moisture retrieval. The second is the use of dual-frequency, single-polarisation, interferometic SAR, to recover forest parameters such as height and biomass. Current research activities in both these applications of microwave remote sensing will be presented.

About the Speaker

Mark L. Williams was born in Kent, U.K., in 1961. He received the B.Sc. degree in physics with computing and the Ph.D. degree in physics from the University of Kent, Canterbury, U.K. in 1983 and 1987, respectively. He has occupied teaching and research positions at the University of Kent, Universiti Brunei Darussalam, the National University of Singapore, and the University of Sheffield, where he first began work in radar remote sensing at SCEOS in 1994. He moved to the Defence Research Agency (formerly the RSRE), Malvern, U.K., in 1996 and worked predominantly on Synthetic Aperture Radar and the theoretical modeling of microwave backscatter. Moving to Australia in 2002, his research there led to the development of a radar imaging model for mixed-species forest
in Australia, used to predict the utility of future space-borne SAR systems. In April of 2006 he began work as an independent scientific consultant in radar remote sensing, and has since worked on the development of a forest SAR computer simulation as an educational and rsearch tool for the European Space Agency’s PolSARPro software package (, and for Australia’s Defence Imagery and Geospatial Organization on terrain-mapping using interferometric SAR. His current interests include SAR calibration, the exploitation of polarimetric SAR data, and the recovery of soil moisture using compact-mode polarimetric SAR.