From soil map to digital database: land resources inventories, SOTER and its applications

Readily accessible information of up-to-data geo-referenced land resources is being requested with increasing frequency. This demand comes not only from the traditional group of researchers on land resources, but also from others such as the environmentalists using land resource data for their modeling (e.g. global change). Increased data storage capacity, faster processing speeds, improved database management and the use of geographical information systems have made it possible to provide more information in a shorter time, at lower costs and in formats suited to the need of the user. In many cases traditional soil survey reports with maps, as common in the past, have been replaced by tailor made databases, which stores profile information linking it only to the polygons of the soil map. A more comprehensive approach is making use of a relational database management system and geographic information system (GIS) linking the soil and land attributes to its spatial distribution. This has resulted in the development of the SOTER methodology (Soil and Terrain digital database) for storage of land resources attribute data in a database system, which is linked to `mapping units`, the SOTER units. These units are defined on their unique combination of terrain and soil characteristics. Once the SOTER units are defined and described in the database the information can serve for all kind of interpretations and assessments such as land evaluation, erosion risk assessment and, for production assessments and modeling. The SOTER methodology is standardized; it describes most attributes according to the Guidelines for Soil Profile Description (FAO, 1990) and the legend of the Soil Map of the World (FAO, 1988). The present SOTER database has the possibility for soil classification inputs, not only according to the FAO-1988 version and WRB (1998), but also for a national classification system. The link of the database to geo-referenced SOTER units makes it possible to produce thematic maps in formats suited for different users