Biomass Retrieval Using P-Band Polarimeric Sar Data: the Biomass Mission
Le Toan, Thuy1; Ulander, Lars2; Villard, Ludovic3; Soja, Maceij4; Saatchi, Sasan5
1Centre d'Etudes Spatiales de la Biosphère, FRANCE; 2FOI, SWEDEN; 3CESBIO, CNRS-CNES-Université Paul Sabatier-IRD, Toulouse, FRANCE; 4Department of Radar Systems, FOI, Linkoping, UNITED KINGDOM; 5JPL, UNITED STATES
The BIOMASS mission is designed to map the full range of the world's above-ground forest biomass, and to quantify biomass changes during the mission lifetime, with accuracy and spatial resolution compatible with the needs of national scale inventory and global carbon flux calculations. This objective is achieved with the P-band SAR. The P-band biomass measurement concept was first based on previous work over the past two decades. During the preparatory phase, six new campaigns have been conducted to address remaining questions on the biomass retrieval algorithms, mainly over tropical and boreal forests, which comprise 75% of the world’s forest cover. The collected datasets comprise the accurate and complete sets of in situ data and P-band SAR data in different modes (Polarimetry, Pol-InSAR and Tomography). This paper will present the exploitation of Polarimetric SAR (PolSAR) for forest biomass recovery. Early works have already demonstrated that P-band PolSAR data could be related to above ground biomass (AGB). Analysis over the recent data sets whaving a large range of forest type, structure, and biomass range reveals similar power-law relationship between backscatter and AGB, and points out the effects of forest structure, and environment factors such as topography and soil moisture variations. Because of differences in backscattering mechanisms prevailing in tropical and boreal forest sites, the inversion algorithms used to recover biomass from PolSAR data have been designed to mitigate or correct differently for environmental effects. The inversion algorithms have been applied to campaign data and analysis has been carried out to simulate performances in spaceborne conditions (including resolution, radiometric stability, ambiguity..). It was demonstrated that PolSAR can provide the initial biomass mapping, but the joint use of PolSAR with PolInSAR and TomoSAR will improve the results towards the required accuracy in biomass retrieval (±20%).