Geographic Information Systems: An Introduction, 3rd Edition

15.2 Spatial Interpolation and Proximity Operations

All GISs support some form of proximity operation, in which attribute values are assigned to new points on the basis of the values of existing neighboring points or observations. In ordinary circumstances, proximity manipulations (which include topographic functions associated with manipulations in digital terrain models) involve routines for area search and interpolation.

Search operations take place within a specified area, usually from a defined position to a new point, as within a circle around a point (Figure 15.6). Existing attribute values within the area are treated in accordance with the criteria for determining the values of new points. The procedure for proximity operations usually comprises four main steps:

1. Identify a base point.
2. Define or compute the search area.
3. Select or search for objects.
4. Manipulate the attribute data in accordance with the selection criteria.

The manipulations of attribute data may comprise statistical computations, including:

Figure 15.6

An area search operation can be carried out from a given point and within circle of a given radius.

• The sum of all values
• The average of values
• The greatest or least value
• Interpolation of values from those of neighboring objects
• Identification of the most frequently occurring value
• Statistical distribution of values

Area search and the subsequent computation ...