Speaker
Description
Azimuth terrain slopes induce a rotation of the polarimetric SAR (PolSAR) response of environements, which may significantly affect the retrieval of bio- and geo-physical properties through polarimetric approaches that do not compensate for this effect. Besides its obvious use for polarimetric data compensation, the Polarization Orientation Angle (POA) may be employed to characterize the topography of bare soils, as shown in [Schuler 1996].
Several studies [Lee 2003] have reported that the POA can be measured accurately over bare soil, whereas its estimation is, in general, markedly affected by the presence of volume scattering. Strong volume contributions, whose polarimetric structure remains invariant under rotation around the radar line of sight, mask out the orientation-sensitive part of the signal and make the overall POA estimation process less reliable.
In this context, the BIOMASS mission represents an opportunity to acquire information on the topography of terrain lying beneath forest cover. P-band SAR signals penetrate deeply into dense forests and generate strong returns from the ground. Reliable POA estimates could be used as prior information for DTM retrieval in dense forests, and could help mitigate artefacts related to complex phase screen compensation.
This study explores the potential of the BIOMASS mission for POA estimation through the following three steps:
- Evaluating the quality of POA maps computed from BIOMASS data for various land cover classes and terrain slope conditions. This analysis is carried out by comparing estimates obtained using the circular polarization algorithm [Lee 2003] with reference data derived from airborne laser scanning.
- Establishing a theoretical framework to forecast POA estimation reliability from the acquired PolSAR data. This step builds on elements of estimation theory, as well as on the identification and analysis of polarimetric scattering mechanisms.
- Evaluating mitigation strategies based on single and multi-baseline InSAR volume cancellation techniques.
This study is conducted using BIOMASS acquisitions over several test sites, in South America and Africa, together with reference lidar data.
D. L. Schuler, Jong-Sen Lee and G. De Grandi, "Measurement of topography using polarimetric SAR images" in IEEE Transactions on Geoscience and Remote Sensing, vol. 34, no. 5, pp. 1266-1277, Sept. 1996, doi: 10.1109/36.536542
J. S. Lee, D. L. Schuler, T. L. Ainsworth and W. . -M. Boerner, "Polarization orientation estimation and applications: a review" IGARSS 2003. doi: 10.1109/IGARSS.2003.1293798.