Accessibility

In spatial analysis, more than just properties of the analyzed objects are of interest. Especially the relations between them are of interest. As discussed in the lesson "Spatial Query", various relations between objects can be analyzed. There are thematic (or semantic), spatial and temporal relations established. The spatial relations can be divided into topological relations, directional relations and distance relations. In this lesson, the distance relations are of interest. Using methods to detect distances and proximities, answers to the following questions can be given:

• Which is the nearest railway station?
• How many pharmacies are within a radius of 300m from a specific location?
• Which is the best residential area, in the case that the distance to the kindergarten, the school and the shopping centers should be minimal?
• How many people live in the catchment area of the shopping center?

In a GIS the spatial objects are generally (in the two dimensional case) represented by the geometric primitives such as points, lines and polygons and can also exhibit descriptive properties (attributes). In the first unit the basics of distance relations are introduced (unit: Space-Object-Distance Relation). The calculation of the distance relations is discussed in unit 2 (unit: Unlimited Analysis of Distance Relations). Another lesson about accessibility illustrates methods for the characterization and analysis of networks (Intermediate Accessibility).