GIS Files 6: Expert GIS concepts

6.3: Spatial databases (4)

GIS and databases

As previously mentioned, many implementations of GIS use a database rather than simple files for the data storage. Geographical datasets can be extremely large and so the benefits of database storage are as applicable to GIS as to any other kind of system. The elements of data security, the ability to cope with large data volumes and the accessibility to multiple users are equally important. The explosion in the availability of cheap, high-volume disk space has fuelled the proliferation of large databases.

Many large organisations maintain vast enterprise-wide information systems that incorporate different types of geographical objects. For example, a utility company will use GIS to store information about its pipe networks, the location of its customers and the location of its maintenance teams. This information will need to be continually updated as it is much easier to lock the record for a single feature, perform edits and then perform the update if the features are stored in a database rather than in a file. The database also allows the various departments to view the information in different ways.

All major GIS software vendors provide tools to enable database storage. Database management can be a complicated and specialist task, so products are developed to provide a user interface similar to that of a regular desktop GIS but which also handle the database administration side. Such products are often referred to as middleware. Middleware is usually designed to operate across a range of the most popular database products such as MS-Access, SQL Server, Oracle®, Sybase®, Ingres® and IBM®. More recently, the database software companies themselves have been producing extensions to the standard functionality that allow for the storage of complex data types, for example, coordinate geometry, raster images and terrain models. This is a telling sign of how GIS has become recognised as a key component of information technology.

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