Geographical Information Systems (GIS) are a means to handle the increase of available geographical information for describing environment. Two types of GIS : the multi-purposes ones covering large geographical areas such as a nation, and those more local having a limited scope. Though the concept in structure is the same for both types, creating and handling local GIS is easier. This work focus on local GIS and three examples are given. The first example deals with a preliminary impact study in the National Park of Mercantour. Data held in the GIS are used as binary filter to select favorable areas. The second GIS deals with the benthic communities along the French Mediterranean coast. The scope is to synthesize data acquired on the same sites but by different measuring techniques by different researchers at different instants. This calls on a concept of reliability of the available information. Associating a GIS with a numerical model simulating changes in urban area is the third example. The model takes into account constraints due to local environmental conditions given by the GIS and external sources of population. Results are forecasts for 2000 and 2025 of the changes in population for various scenarios, in the area of Toulon (Var).
