Use of GIS and remote sensing for soil mapping and for locating new sites for permanent cropland — A case study in the “highlands” of northern Thailand

Until a few decades ago, the highlands of northern Thailand were predominantly under forest. Since then, a growing pressure on the land, partly from hill tribes living in the highlands, has led to rapid deforestation and land degradation. To counteract these problems, the Royal Thai Government started a “Highland Development Project” in 1990. Activities of this project include soil inventories and the use of soil and other data to locate new sites for cropland and settlements for hill tribes. In this paper, a case study is described in which the use of a Geographic Information System (GIS) and digital remote sensing methods is compared with the methods currently used in these activities. The GIS is used for the preparation of a terrain mapping unit (TMU) map which integrates data from existing maps and data interpreted from satellite images. The GIS is also used (i) to derive relevant information from the TMU/soil map (e.g. land suitability and estimated erosion rates) and (ii) to integrate this information with land cover/use and accessibility information. This integrated information is used to locate physically suitable, accessible and not yet used areas that could become potential new cropland sites for highland people after resettlement.

A comparison between the currently used methods and the GIS methods shows that apart from considerable time savings, also improvements in data quality are achieved, e.g. by the preparation of a slope map based on a digital terrain model and by up-dating of existing land use information with satellite imagery. The spatial and attribute data base in the GIS makes it possible to use the original, non-aggregated data and, in addition, facilitates the integration of the various data for the analysis of potential sites for resettlement according to various criteria and objectives.