The following classes of GIS data may be distinguished:
- vector data: the features of interest are represented by points, lines or polygons. The vector format is suitable for discrete features like roads, buildings, (coastlines) or land ownership patterns. Design software packages (e.g. AutoCAD) work almost exclusively with vector data. The difference to GIS vector data, however, is that the latter carries geographically meaningful coordinates.
- raster data: the data consists of a regular grid of cells, comparable to a digital image. Actually, raster data are just an image with a spatial reference assigned. Raster data formats should be used for all themes carrying spatially more or less continuous information which cannot easily be converted into discrete units should, e.g. satellite imagery or digital elevation data.
In general, each software package has its specific formats for vector and raster data. These formats are sometimes, but not always compatible with other software packages and shall not be discussed in detail in this place. However, there are some formats readable by virtually all packages and therefore best suitable for data exchange.