Defining Suitable Areas by Selection, Exclusion, Buffering and Overlay - Principles and General Procedures


Step 1:
The first step in the process requires that the planner defines precisely the planning issue and the area of interest (i.e. in the forestry sector the planner wishes to define the forest cover)

Step 2:
The selection criteria that have been set need to be discussed with other experts or with other people working in the relevant sector. In some cases it may be necessary to discuss the criteria selection with the general public (i.e. areas that are to be classified as having a low potential. In this case the criteria defining what constitutes a “low potential” needs to be discussed).

Step 3:
The data that is needed for the mapping process has to be acquired. It may be necessary both to acquire the spot data as well as the map data. This may require that topographical maps have to be digitized.

Step 4:
It may prove necessary to reclassify a copy of the digitized map data according to previously defined criteria.

Step 5:
The criteria need to be adjusted according to the available map data. It may also be necessary to refine the criteria, this should be done in an iterative process.

Step 6:
A flow chart has to be developed that defines the exact technical procedures that need to be undertaken. The technical procedures include defining which criteria / procedure has to be applied to which layer in order to get a layer or an intermediary (or final) result of the analysis.

Step 7:
The GIS overlay or other procedure is then undertaken in accordance with the steps defined in the flow chart developed during step 6.

Step 8:
Finally, the planner prepares a presentation of results (or options) and these are then given to the decision-makers, general public, etc who are then expected to undertake action accordingly.