The deployment of a Geographic Information System (GIS), regardless of size or ambition, requires the implementation of a project, which is the mobilization by a group of individuals or collectives of resources available in a given time and in terms of objectives and specific means. GIS is an information system, its resources being of four types: physical resources (servers and networked computer workstations, devices for measurement and restitution), software resources (GIS software, data entry, remote sensing, cartography and drawing …), informational resources (data types…) and human resources (individuals, groups …).
Although GIS projects vary widely in objective and by nature, once the objectives of the project are set, they all follow more or less the same number of well-defined steps (see figure): inventory and collection of the necessary data, organization and coherence of these data, transformations, combinations of these data and production analysis, shaping the results into cartographic and statistical form.
The collection phase or data entry is important. A reflection on the level of detail of vector entities and the resolution of spatial raster data is essential for a successful project. These choices are directly related to the scale of the project, that is, the extent of the study area and the nature of the problem and its transcription. For example, if the objective is to determine the sites of a certain area, it is important that the level of detail and resolution of the data is high enough to characterize the desired site. Care must be taken regarding the fact that it is the layer at the lowest resolution that determines the resolution of the analysis.
The choice is often limited by the actual data available or realizable, and its cost. The volume of data is also a constraint. Whether raster or vector, increasing the level of detail or resolution of the data implies a significant increase in RAM memory resources, or massive and sometimes prohibitive increase in computation time.