Speaker
Description
The launch of the European Space Agency’s BIOMASS mission, the first spaceborne P- band SAR mission, opens new opportunities for characterizing forest ecosystems from a low-frequency radar perspective. The long wavelength of P-band signals enables significant penetration through the forest canopy, providing information on the vertical distribution of above-ground biomass and on the underlying terrain. In particular, the retrieval of the ground scattering contribution enables the generation of Digital Terrain Models (DTMs), a product traditionally derived from airborne LiDAR measurements, which provide high accuracy but are limited in spatial and temporal coverage.
This work presents a complete processing chain for the generation of forest DTMs from BIOMASS tomographic data. The proposed approach addresses the main challenges associated with exploiting interferometric phase information in forested environments. These include the calibration of the interferometric phase to mitigate ionospheric disturbances, the estimation and removal of unknown phase offsets between acquisitions due to residual atmospheric effects, and the identification of an equivalent phase center for vertically distributed scattering that preserves the geometric consistency required for phase triangulation. A dedicated separation of ground and volume scattering contributions is then performed to isolate the phase associated with the terrain surface and retrieve the underlying topography. Finally, a quality index is computed to quantify the ability of the algorithm to explain the observed phase in terms of the underlying model.
The resulting DTM is validated against airborne laser scanning (ALS) measurements provided through the GEO-TREES initiative, which offers high-resolution DTMs and biomass reference data. The comparison demonstrates good agreement between the BIOMASS- derived terrain elevations and the ALS ground reference, highlighting the potential of P- band tomographic observations for terrain retrieval beneath forest canopies. These results demonstrate the feasibility of deriving accurate DTMs from BIOMASS data and represent an important step toward exploiting the mission’s unique capability for simultaneous characterization of forest structure and underlying terrain at continental and global scales.