Intercomparison of Electromagnetic Scattering Models for Delay-Doppler
Maps along a CYGNSS Land Track with Topography
Abstract
A comparison of three different electromagnetic scattering models for
land surface delay-Doppler maps (DDMs) obtained from global navigation
satellite system reflectometry (GNSS-R) along a Cyclone Global
Navigation Satellite System (CYGNSS) track in the San Luis Valley,
Colorado, USA, is presented. The three models are the analytical
Kirchhoff solutions (AKS), the Soil And VEgetation Reflection Simulator
(SAVERS), and the improved geometrical optics with topography (IGOT).
Common inputs to the three models were defined by using field samples of
soil moisture and texture, soil surface roughness measurements, and a
digital elevation model (DEM). The resulting peak reflectivity profiles
of the models and the CYGNSS data all had a dynamic range of 10 dB along
the selected track, mainly due to the influence of topography. The
reflectivities obtained from all three models agreed with one another to
within 2.4 dB along the full length of the track. The models also showed
general agreement with the corresponding CYGNSS data, although the
modeled profiles were higher and smoother. Additional characterization
of fine-scale surface roughness is identified as an area for future work
to improve model fidelity. An intercomparison of DDM structure for three
selected acquisitions is also provided.