Remote Sensing of Coastal Marsh Vegetation Structure using Multi-angle Imaging

This study explores using a remote sensing technique based on imagery from multiple viewing angles that retrieves leaf area index (LAI) for coastal marsh vegetation. The method uses data from spaceborne instruments with high spatial resolution (~20 m) and multi-angular imaging, specifically the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) aboard the NASA spacecraft Terra or the Compact High Resolution Imaging Spectometer (CHRIS) aboard the Project for On-Board Autonomy (Proba). Off-nadir views are shown to provide information about the marsh canopy structure, which is mostly comprised of grasses, sedges, and rushes in moderate to high saline regimes. Water strongly affects the bi-directional reflectance distribution function (BRDF) for wetlands and cannot be handled by inversion of conventional canopy radiative transfer models. The first objective of this study was to extend current methods to account for the non-Lambertian, aquatic substrate. The methodology was then validated and tied to remote sensing instruments (e.g., ASTER and CHRIS) through ground truth. Initial study targeted sites in the Chesapeake Marshlands National Wildlife Refuge Complex. However, it is also likely that the techniques and products of this and future work will be widely applicable to assessment and monitoring of marshes globally and is the first step to develop models for other types of wetland.