COMPARISON OF SPOT5 AND LANDSAT7 FOR FOREST AREA MAPPING

The main purpose of this study is comparison of the potential of the Landsat7 ETM+ data and SPOT5-HRG image for forest area mapping at the scale of 1:25000 in northern of Iran. A Landsat7-ETM+ image and SPOT5-HRG in Pan and XS modes, with the spatial resolution of 5 and 10 meters, were analyzed. The images were almost simultaneous. The investigation on the image quality showed that there was a non-systematic misregistration between SPOT5-Pan and SPOT5-XS. There were no other noticeable radiometric and geometric distortions. Orthorectifications of the both satellite data were implemented using ephemeris data and a digital elevation model. The geocoded images were checked for reliability in comparison with the digital topographic map. Diverse suitable spectral transformation such as rationing, PCA, and Tasseled Cap transformation were performed on the images. To generate effective multispectral bands with better spatial resolution, the green, red and near infrared bands, which lie in the spectral range of panchromatic band, were fused with Pan using DIRS method as a radiometric approach. In order to estimate the potential of the satellite data precisely, a ground truth was prepared using aerial photographs. In this relation, 38 black and white aerial photographs at the scale of 1:7000 were taken especially for this project. These airphotos were orthorectified and interpreted. Image classifications were performed using supervised and a new hybrid approach (digital and visual). At first, the images were classified using maximum likelihood classifier without any knowledge of a-priori possibilities. The bes