Quantifying the variable effect of Wind on inSAR measurements of forests
Michael
Lee
Benson, Univ of Michigan, mlbenson@umich.edu
Kamal
Sarabandi, Univ of Michigan, saraband@umich.edu
Leland
Emery
Pierce, Univ of Michigan, lep@umich.edu
(Presenting)
The horizontal and vertical (3D) structure of Earth's forested ecosystems are of great significance to their ecological functioning and societal uses. An InSAR approach is one methodology whereby a forest's structure and height in particular can be successfully estimated. Critical to the successful estimation is a high correlation between multiple SAR images, whether real or simulated. Regardless of a forest's location on the Earth, wind has a significant effect on a forest's appearance to an L or C-band SAR system and thus induces a level of decorrelation in the formation of the synthetic image as well as products of synthetic images, such as interferograms and terrain height estimates.
In order to investigate and quantize the decorrelation induced by a wind field, we have developed a model for the repeat-pass interferometric SAR response of a forest including the application of a wind field. The simulation consists of multiple interconnected pieces including the generation of fractal tree geometries, a wind simulator to apply variable wind forces to the generated trees, an electromagnetic model toallow us to calculate a single look complex approximation of the backscattered electric field for the trees, an image forming technique based on antenna array theory, and an image processing algorithm.
Results present polarimetric coherence as a function of incidence angle, wind speed, and ground elevation angle. An important feature of this research is the usage of a physically-based realistic wind model that is based on measurements of wind effects on trees as well as realistic models of fluid flow and simple harmonic branch segment resonators. Allowing branches to bend and move out of the plane of the incident wind field enables our model to capture numerous features of a physical tree blowing in the wind. This physical model is necessary for a realistic simulation of the effects that wind has on a given InSAR imaging system as expressed in this study by the interferometric coherence as well as the relative error in scattering phase center for an interferogram.
Presentation Type: Poster
Poster Session: Carbon Cycle Science
NASA TE Funded Awards Represented:
Sarabandi, Kamal
VEGEX3D: LiDAR-SAR/InSAR Extrapolation and Simulation Models for Retrieving Vegetation 3D Structure and Biomass