Defining Suitable Areas by Selection, Exclusion, Buffering and Overlay - Advantages and Limitations

More criteria can be presented and used during the planning process, making the search for a decision more transparent (e.g. especially during participatory planning exercises) The information generated can be used in order to develop different planning scenarios, which in turn provides decision makers with different options to choose from. A multitude of functions can be undertaken within a short period of time and with comparative ease using the GIS technique. The computer can calculate complex interrelationships rapidly and the product can be depicted in a visually appealing manner for decision-makers. Improved criteria can be defined once information in the GIS has been visualized and linkages between various map layers or features have been established. The new criteria will improve the overall information available for the decision-makers and will (hopefully) improve the consensus that they reach.

The information selected for the criteria has to match with available map data in order to apply the method. If map data is not available then it is necessary to painstakingly acquire / digitize the relevant map data first before the next step can be undertaken. This can be a time consuming and costly task. Defining appropriate selection, exclusion or buffering criteria often proves to be quite difficult. Generally speaking, the result produced by the GIS is only as good as the quality of the previously selected criteria. Therefore, planners must be familiar and practiced in defining the most appropriate criteria. Poor quality data (including map data) may lead to the production of inaccurate maps. The criteria used can often be defined in a rather subjective manner