RELATIONSHIPS BETWEEN PHYSICAL CHARACTERISTICS AND POLARIMETRIC RADARBACKSCATTER FOR CORSICAN PINE STANDS IN THETFORD FOREST, UK

Global monitoring of forest extent and changes of extent with time are vital not just to provide a continuous assessment of a renewable reso urce essential to mankind but also to give an input to models of the g lobal carbon cycle and of climate change. Microwave remote sensing is a potential means to accomplish this objective. However, to determine the optimum characteristics of a satellite synthetic aperture radar (S AR) for reliable forest monitoring it is first necessary to validate m odelled microwave backscatter relationships in studies of relatively s mall areas using data from aircraft SAR systems and from detailed grou nd survey. The Maestro 1 Campaign provided fury polarimetric SAR data in three wavelengths together with a large set of ground data for Thet ford Forest. Calibrated microwave responses were averaged for more tha n 300 stands, primarily of Corsican pine. A georeferenced database for the test site was built up from these mean responses combined with in formation on planting date, species and, for those stands fully sample d, characteristics such as height and timber volume. The radar backsca tter at P and L bands, expecially the cross-polarized responses, corre late well with volume. An analysis is made of the accuracy with which regression models can be used to predict timber volume over larger are as around the test site. The precision of this prediction can be impro ved by fuller use of the information contained within the measured dat a, specifically in the correlation between the HH and VV returns, and by the fuller use of theoretical models, which consider more comprehen sively the complete polarimetric backscatter mechanisms relevant to th e response of stands.