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The study of spatial distribution of forest changes tin the northern forests of Iran
2. Data
The data used in this study were:
- Digital 1:25000 thematic-topographic maps dating 1982 which prepared based on 1:20000 aerial photos dating 1967, according to the FRO order and National Cartographic Center (NCC) supervision. These maps were produced by traditional cartography at first and then converted to digital maps. They have 63 different data layers including: residential areas, roads, rail ways, forests, ranges, gardens, contour lines, etc.
- Digital thematic-topographic maps dating 2001 which prepared based on 1:20000 aerial photos dating 1994, according to the FRO order and NCC supervision. These maps including 276 sheets, have 63 different data layers the same as pervious maps.
- Roads and residential areas maps which were extracted from 1:25000 digital maps dating 2001.
- Forest area maps, which were extracted from 1:25000 digital maps at the start and the end of the period.
- Watershed basins boundary maps.
Fig. 1. Location of the study area
3. Extracting forest maps from 1:25000 digital maps
Forest layers were extracted in Microstation software and then values of 0 and 1 were labeled to non-forest and forest areas respectively in Arcview software. This process was done for all of the map sheets covering each watershed basin for both 1967 (Fig. 2(a)) and 1994 (Fig. 2(b)) years. By comparing forest maps related to the start and the end of the period (1967 and 1994), forest decrease and increase maps were obtained separately in these 4 watershed basins (Fig. 2(c)). These maps having a resolution of 30 meters were imported to the Idrisi software. Among four watershed basins, one of them (watershed basin number 26) is illustrated in figure2.
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