Quantifying the results of wind and rain on ifsar tree height estimation

The horizontal and vertical (3D) structure of Earth´s forested ecosystems are of great significance to their ecological functioning and societal uses. An IfSAR 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. Regardless of a forest´s location on the Earth, wind and precipitation can significantly alter a forest´s appearance to a SAR system operating in either the L or C bands and so too decrease this necessary correlation. In order to investigate and quantize the decorrelation induced by factors such as wind and rain, we have developed a model for the repeat-pass interferometric SAR response of a forest including the application of a wind field and / or a rain storm. The simulation consists of multiple interconnected parts including the generation of fractal tree geometries, a wind simulator to apply apply variable wind forces to the generated trees, an electromagnetic model to allow us to calculate a Single Look Complex value for the SAR return of the combined target, an image forming technique based on antenna array theory, and an image processing algorithm. Results present polarmetric coherence as a function of platform look angle, wind speed, and moisture content. 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 realistic 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.