Modern desktop GIS provide you with many analytical tools to process data into new forms of information. According to Berry (1987) there are four fundamental classes of spatial analysis operations and they can be applied to either a single layer of spatial data or multiple layers of data.
  Single layer Multiple layer

Reclassify

Overlay  
Proximity & connectivity  
Neighbourhood

Of the four classes, reclassification operations repackage existing information on a single layer. A new map value is assigned to an entity as a function of its inherent properties such as initial value, position, size, shape or contiguity. Overlay operations, however, involve two or more layers and compute a new value for every location as a function of the values associated with that location on each layer. If the strength of GIS lies in its ability to integrate spatial data then, perhaps, overlay epitomises spatial analysis in GIS.

Proximity and connectivity operations are more advanced techniques that generate information by characterizing the relative positioning of map features. They create a new map expressing the distance between locations as straight-line length (simple proximity) or as a function of cost (effective proximity). Finally, neighbourhood operations create a new map based on the consideration of values within the general vicinity of target locations. The neighbourhood can be defined in terms of a focal area around a location, in which case the data processing is conducted on a single data layer, or in terms of a district or zone that has been specified from a second source.

As well as considering the range of spatial operators available to the geospatial analyst you should also be aware of the techniques used to prepare geospatial data prior to spatial analysis. In this topic you start by examining these techniques and then learn to process a single layer of entities stored as either raster or vector data model and multiple layers of geospatial data.