Hyperspectral and Polarimetric Signatures of Vegetation from AirMSPI and AVIRIS Measurements

Abstract:

Leaf scattering spectrum is the only optical variable that conveys information about leaf biochemistry. It cannot be directly measured from space because the radiation measured by the sensor is affected by the canopy structure and the atmosphere. Multiangle remote sensing data provide information critical to account for such effects, including structural contributions to measurements of leaf optics. Some radiation is scattered at the surface of leaves, which contains no information on the leaf interior. This represents an additional confounding factor, unless it can be accounted for. Polarization measurements are useful to quantify leaf surface characteristics because radiation scattered at the surface of leaves is partly polarized whereas that from the leaf interior is not. This poster presents analyses of surface reflectance data from Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) and the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). Our results indicate that 1) sensitivity of spectral reflectance corrected for canopy structure effects to foliar nitrogen (N) content is negatively related to the leaf degree of linear polarization (DOLP); 2) polarized canopy BRF (pBRF) in oblique directions can account up to 52% of reflected radiation; 3) pBRF varies with species, suggesting that leaf surface properties cannot be neglected when interpreting BRF; 4) canopy reflects radiation specularly in all directions. In general our results suggest that hyperspectral, multiangle and polarimetric data are required to monitor leaf biochemistry from space.