Potentiality of ASTER Images For Forest Density Mapping in Zagros
The potentiality of ASTER images from the Marivan city forests, dating June 2003, for forest density mapping in Zagros investigated. The aerial photographs (1:20000) dated September, 2004 were used for generating thorough ground truth map. Images hadn't any radiometric error. The geometric correction of images and photographs was implemented using Orthorectification method with RMSE<1 pixel. The ground truth map, which included four classes [(5) 5-10%, (4) 10-25%, (3) 25-50% & (2) 50-75%], using dot grid was prepared. Different synthetic bands from rationing, principal component analysis and suitable vegetation indices were created, to employ in further digital analysis, together with the original bands. The data classified based on four classes by supervised method with the Maximum likelihood, Minimum distance to mean and Fuzzy algorithms using synthetic and origin bands. The highest overall accuracy and kappa coefficient equal to 65.5% and 48.7% obtained with Maximum likelihood algorithm and 6 bands set. The highest spectral similarity was between the 4th and the 5th classes. On the other hands, class no.5 had little extent in study area. So, classes 4th and 5th, merged. In three-class classification, the highest overall accuracy and kappa coefficient equal to 68.5% and 51.5% obtained with Maximum likelihood algorithm and 6 bands set. Lack of precious topographic maps and also shade effects on interpretation and analysis were the most important problems. Finally, it can be concluded that resulted accuracy with the data set, processing and analysis that were used was relatively desired.
Keywords: ASTER, Zagros Forests, Density Mapping, Ground Truth, Aerial Photographs, Accuracy.