Results of a case study on importance and application of spacial and geographical data are presented here. Geographical information systems and remote sensing techniques were used to make necessary maps. In this research, processing of satellite images, G.I.S and a capability of these two methods is used for land suitability evaluation in an arid region. This region is part of varamin plain and watershed catchment of jajroud river. Based on the information obtained from the mamazan weather station, the average maximum of highest temprature for the year is 39 oc and the average minimum of coldest temprature for the year is -1.5oc. Average yearly rainfall for the region is 146 mm. Soils in the region are classified in two Aridisol and Entisol orders (U.S.D.A., 1999). Despite topographic conditions which are often flat, slope and hypsometric maps were produced (method to increase the accuracy of research) using geographical information system. Furthermore, descriptive information and main characteristics of land units (obtained from slope, hypsometric and soil maps) for every land utilization type was generated using the capabilities of the geographical information system. Agreement ratio between soil map derived from digital classification with maximum likelihood method and ground truth map derived from traditional methods and its Kappa index were 82% and 75% respectively. Analysing the matrix error in this research shows that unit 2 has not well deliniated from unit 6 (deliniation of Haplocalcids from Haplocambids), because unit 2 is covered with plants. This can be identified from the area difference between these two units of digitalized map and ground truth. Also, it seems that user’s accuracy factor is more important than producer’s in evaluation of digitalized maps’accuracies. The results show that qualitative suitability class for land mapping units of the region in current conditions for wheat and barley are often S1 and S2 and for some units S3 and N. For cotton and maize they are S2, S3 and N for some units, which can be increased by solving some important problems such as soil fertility limitations.
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