Research objectives and content
The objective of this project is to develop methods of monitoring of changes in forest environment, by radar remote sensing. More specifically, innovative approach using phase information provided by airborne and spaceborne earth observation radar systems is investigated. The motivation arises from the fact that modulus quantities such as the backscattering coefficient of forests covers, have only a small variation range, limiting considerably parametric inversions and classifications. On the other hand, the phase sensibility to seasonal variations, climatic conditions, or vegetation growth is very important. Up to now, the phase has mainly been used in interferometric observations. This requires two complex data sets (reconstructed pictures). Individual phase also offers practical interpretations, as illustrated by a study of the grant candidate, from ERS1 data, in a tropical forest. Furthermore, it is projected to examine the interpretability of the phase of the original echoes (raw data) to improve the information content for an inversion attempt (biomass evaluation, tree species determination, tree height computation, climatic conditions estimation...). This approach necessitates the study of the impact of various treatment and SAR image generation methods. The use of airborne (DOSAR, CARABAS) and spaceborne (ERS1-2, JERS1, RADARSAT, SIR-C) data at different frequencies has the great advantage to allow the measure of the influence of different forest types, as the penetration depth varies with frequency. This, of course, increases inversion and discrimination possibilities.
As far as the phase information is concerned, the coherence measurement and the interferograrn correlation for various trees species and soil types or vegetation is of prime importance, and can be used for a classification attempt. Supplement advantages result from the use of different polarizations, incidence angles, and resolutions (physical or reconstruction limitations).
The study will be performed within the framework of the EUFORA project (EUROPEAN Forest Observations by Radars), a fourth PCRD in the Environment and Climate Programme, Topic 3.1.1 Research and Development Project for 'Space Techniques applied to environmental Monitoring and Research ' (1-9-96 to 1-9-98).