Topographic normalization of Landsat TM images in rugged terrain

A topographic correction method has been developed for TM images of rugged terrain, using ASTER stereo image pairs as a key input. The difference in solar radiance as a result of topography has always been a major barrier to the research on quantitative remote sensing in rugged areas. The mountain radiative transfer model with strict physical meaning must be selected to eliminate terrain effects. However, its development are restricted owing to its stringent requirements of high precision and resolution for digital elevation model DEM; it is desirable that the spatial resolution is 0.25 times the pixel size or finer, and moreover, DEM data are difficult to be obtained actually. Therefore, both SRTM data and ASTER GDEM have failed to meet the accuracy requirements for the Landsat TM. By comparison on DEMs with three resolutions, 15m, 30m and 90m, the results suggest that 15m DEM has topographic effects removed effectively. Based on ASTER stereo image, 15m DEM data with relatively high accuracy in the study area were collected consequently. On this basis, micro topographic factors, such as slope, aspect, shield factors, and the sky visible factors, were derived. The main atmospheric parameters were obtained by taking the spectrum curves of several typical objects into consideration. Finally, TM image terrain correction was rapidly completed, by applying topographic factors and atmospheric parameters to Richter mountains radiation models. The results indicated that this method could remarkably remove topographic effect, and also provide basic data for surface parameters retrieval of quantitative remote sensing in the rugged terrain.