Assessing Desertification in Ardakan Area Using Remote Sensing

摘要

More than one-third of land in the world is locate in the areas whit arid and semiarid climate and desertification has increase in these areas during recent decades. Around 80% of Iran is located in arid and semiarid areas. Sand dunes as an indicator of desert land cover an area about 32 million hectare. Among which 12-mil hectare has not been stabilize yet. Advancing moving sand dunes has resulted in much damage to agricultural products and urban areas. In this survey satellite images and aerial photos are use to evaluate the role of land use changes on desertification in 1955, 1997 and 2002. To do so, IRS image of 2002 and available aerials photos of 1955 and 1997 are used. Following making the aerial photos mosaic processing was done using ILWIS software. Needed data was completed by field surveying and the land use map was produce for the two years. To produce the land use map using digital processing methods 10 sample set (training points) were selected uniformly in the area. After, preprocessing including geometric correction, image enhancement, band composition and etc, image classification was done by maximum likelihood method and the land use map was produced. In this phase, obtained land use map was corresponded to the ground truth map which was achieved by field surveying and recording coordinate of points whit GPS pixel to pixel and accuracy obtained from numerical classification estimated to be 45.3%. Then due to do obtained low accuracy, the visual method used to produce the land use map so the accuracy of 78.5% achieved. Finally, the area of each land use and the rate of changes were calculated. The results indicate a decrease of 2000 ha in the area of the desert land from 1955 to 1997 and of 160 ha from 1997 to 2002 and an increase in the area of the other land uses. Results show no desertification in the study area, even though land degradation can obviously be identified in the area, which is resulted from the changes of gardens, and agricultural land uses to industrial and urban areas.