3.3.4 The geometry
In a GIS, data appear as geometries and tables and are represented in different ways depending on the data type. Three types of geometries exist to represent geographic objects:
- Points to represent point features (cities, projects, water points, etc.)
- Lines to represent linear objects (rivers, roads, etc.)
- Polygons to represent area elements (municipalities, zoning, land use, etc.)
Geometries in a GIS
The choice of geometry to represent data can vary depending on the scale of visualization.
For example, it is preferable to represent hospitals on a map of France by points. On the other hand, at the scale of a district, one can use polygons to represent the ground area of the hospital buildings.
Varied use of geometries for the same data