What is GIS?

• What is a geographical information system (GIS)?
• What is the use of GIS for the Netherlands Court of Audit?
• How can geographical information be used?

What is a geographical information system (GIS)?

A geographical information system shows not only data about a certain location on a map, but can also be used for analysing and relating different kinds of data by location (so called data layers). Examples of location data on a map are postal codes; longitudes and latitudes; countries, provinces, municipalities, neighbourhoods and streets.
A lot of data used for policy making are fixed to a location. These data are not just about the environment or spatial planning, but also about education, health (care), employment, crime and development aid.

These data or information layers can be connected to eachother based on their location. This may lead to new information that without a GIS would not have been traced easily.
A special kind of geographical information is data derived by satellites or by aerial photography.

With GIS an auditor can:

• link his own data and that of others to maps;
• make complex calculations and display the results on maps;
• query information about topics to show the differences or similarities between  locations;
• analyse whether a relationship exists between the data by combining other data layers on a map;
• discover trends over time;
• present his audit results in an attractive way.

What is the use of GIS for the Netherlands Court of Audit?

The Netherlands Court of Audit uses more and more geographical information in her audits. For example to gain insight into financial and non-financial policy information. Geographical information makes it possible to:

• map risks;
• design and conduct an audit;
• analyse the audit results.
• visualise the audit results in an attractive way.

How can geographical information be used?

The following steps are important when using geographical information:

• Collect the necessary data. A lot of geographical information is already available from public and non-public sources.
• Convert the data in a GIS file format (optional). Generally, GIS data from government agencies are stored in common file formats. Most GIS software can read and edit several file formats.
•  the data. The collected data should be reviewed and approved based on a few predetermined quality criteria as source, timeliness, completeness, method of measurement.
• Combine the data. The great strenght of GIS lies in the ability to combine data layers.
• Relate and analyse the data; GIS has an added value in relating and analysing data based on their location.
• Present the results. Geographical data can be presented in several ways:

- on paper or digital maps;
- in a more dynamic way by providing the user the opportunity to turn on and off several data layers.