GIS Software

Software that is used to create, manage, analyze, and visualize geographic data, that is, data with a reference to a place on Earth, is usually denoted by the umbrella term geographic information system (GIS) software. Typical applications for GIS software include the evaluation of places for the location of new stores; the management of power and gas lines; the creation of maps; the analysis of past crimes for crime prevention; route calculations for transport tasks; the management of forests, parks, and infrastructure such as roads and waterways; and applications in risk analysis of natural hazards and emergency planning and response. For this multitude of applications, different types of GIS functions are required, and different categories of GIS software exist that provide a particular set of functions needed to fulfill certain data management tasks. This entry first explains important GIS software concepts; then it lists the typical tasks accomplished with GIS software and describes different GIS software categories; finally, it provides information on software producers and projects.

GIS Software Concepts

To represent a geographic object in a GIS, for example, a building or a tree or a forest, a data representation has to be established first. GIS usually provides two different possibilities to represent a geographic phenomenon: the raster representation and the vector representation. In the raster [Page 1319]representation, a regular mesh of cells is used, where every cell records the value of the attribute that describes the phenomenon—such as the red/green/blue values in a digital image. Rasters are typically used to represent variables that are continuous over space, such as terrain elevations or land cover. In the vector model, which is commonly used to store objects that are spatially discrete, every object is represented by a (vector) geometry (e.g., a point, a line, or a polygon) and by value fields that describe the nonspatial object properties, the so-called attributes, in a table. For instance, a building might be represented by a rectangle geometry and have attached two fields that describe the construction year and the owner.

Figure 1 A typical desktop GIS user interface with map view, layer view, attribute view, and tools for navigating and exploring data, as well as tools for creating and modifying geometries

Source: Stefan Steiniger.

In GIS software, geographic objects that have the same geometric and attribute representation are typically grouped in so-called layers to simplify data management tasks. For instance, all buildings that are represented by polygons and have information on owner and construction year are grouped in a layer labeled “buildings.” Figure 1 shows the typical graphical user interface of a GIS software package that includes the concept of geometries (map view) connected to values in tables (attribute view), as well as layers that contain one class of objects (e.g., rivers).