The Capabilities of Terrarar-X Imagery for Retrieval of forest parameters
Publication from Digital
ISPRS TC VII Symposium 100 Years ISPRS, Vienna, Austria, July 5, 2010, IAPRS, Vol. XXXVIII, Part 7B , 1/2010
The TerraSAR-X mission was launched in June 2007 operating a very high resolution X-band SAR sensor. In Spotlight mode images are collected with 0.75m GSD and also at various look angles. The presented paper reports methodologies, algorithms and results emerged from the Austrian research project Advanced Tools for TerraSAR-X Applications in GMES with emphasis on retrieval of forest parameters. For deriving forest features like crown closure, vertical stand structure or stand height a digital forest canopy model serves as an important source of information. The procedures to be applied cover advanced stereo-radargrammetric and interferometric data processing, as well as image segmentation and image classification. A core development is the multi-image matching concept for digital surface modelling based on geometrically constrained matching, extending the standard stereo-radargrammetric approach. Validation of surface models generated in this way is made through comparison with LiDAR data, resulting in a standard deviation height error of less than 2 meters over forest. Image classification of forest regions is then based on TerraSAR-X backscatter information (intensity and texture), a 3D canopy height model and interferometric coherence information yielding a classification accuracy above 90%. Such information is then directly utilized to extract forest border lines. Overall, the TerraSAR-X sensor delivers imagery that can be used to automatically retrieve forest parameters on a large scale, being independent of weather conditions which often cause problems for optical sensors due to cloud coverage.