Building an accurate GIS database of spatial entities is a time consuming and exacting task. Raw geographical data are available in many different analogue or digital forms, such as maps, aerial photographs, satellite images, or tables. There are four, not mutually exclusive ways to create a digital geographical database:

1. acquire data in digital form from a data supplier
2. digitize existing analogue data
3. carry out one's own digital survey.
4. interpolate from point observations to continuous surfaces (raster models)

 
In all cases the data must be geometrically registered to a generally accepted and properly defined coordinate system. The data need to be converted to the internal database structure of the GIS. With existing digital data sets this often involves using a standard exchange format. Where the original data are in analogue form the coordinates of the entities are recorded digitally using devices such as digitizers, scanners, and stereoplotters. Most GIS provide exchange and data editing tools for this work. Attribute values must also be linked to the entity database, which involves building links to relational tables or spreadsheets. Essential details concerning the origin and other important characteristics of the data are stored in meta data files.