Delineation of northern boundary of Caspian forest using multitemporal satellite images (Case study: Chaboksar forests)

Because in the most cases separation of forest boundary with monotemporal images is not possible, this study was performed with multitemporal images in order to delineate Caspian forests boundaries in Iran (case study in Chaboksar). In addition to deciduous broad-leaved forests there are afforested coniferous evergreen stands, tea and citrus orchards, farms and orchards with deciduas species in the study area. Spot-HRG and Terra-ASTER images from two different dates (14.8.2002 and 28.2.2002) were selected for this study. Radiometric errors were negligible and geometric correction (orthorectification) was precisely applied using digital elevation model. Two images were registered with each other. After defining forest and non-forest classes, the suitable training areas were determined and revised. Separation of forest and non-forest classes was carried out by monotemporal classification, multitemporal classification, hierarchical and digital-visual hybrid approaches. In order to determine the accuracy of maps resulted from interpretation and classifications a ground truth (forest boundary) was prepared using surveying with GPS. The length of selected surveying route was 64.5 km. The results of different classifications were compared with ground truth and their accuracy was determined. Kappa coefficient for classification of growing season and leafless season images, multitemporal classification, hierarchical approach and digital-visual hybrid interpretation were 0.28, 0.43, 0.57, 0.62 and 0.71 respectively. The most and least accuracy were related to digital-visual interpretation and classification of growing season image respectively. Results showed that forest boundary can be separated from non-forests by multitemporal images with high and acceptable accuracy. Based upon knowledge, experiences and the current study it is strongly suggested that leafless season images accompanied by growing season image, should be used in updating process of topographic maps of Caspian forests in such region.