In the preparation of geotechnical maps and plans related to engineering problems, the prompt handling of large volumes of information related to geotechnical data and the results is only possible through the use of software such as the Geographical Information Systems (GIS). Several methods for preparing geotechnical maps exist for engineering. This paper describes the method used in the production of a geotechnical map for the area of Covilhã (Portugal). The ultimate objectives were the creation of a Suitability for Construction Map and the building of a Geo-referenced database, and its development and application in a simple and rapid way, and the production of reliable results that can be used for the administration and support of the planning of the town.