Weighted Linear Combination

A weighted linear combination is an analytical method that can be used when dealing with multi-attribute decision making (MADM) or when more than one attribute must be taken into consideration. Every attribute that is considered is called a criterion. Each criterion is assigned a weight based on its importance. The results are multi-attribute spatial features with final scores. The higher the score, the more suitable the area. A land suitability analysis is an example of a method using a weighted linear combination.

An example of how to use a weighted linear combination is as follows. First, numeric ranges are assigned to a set of continuous criteria. Next, the numeric ranges are combined into a weighted average. The designer then assigns weights directly to each attribute layer on the map. The total score for each option is calculated by multiplying the weight assigned to each attribute by the scaled value given for that attribute to the alternative and then summing the products over all attributes. The scores are calculated for all of the alternatives and the attribute with the highest score is chosen. This method can be used in any GIS system that has overlay capabilities, and allows the evaluation criterion map layers to be combined in order to determine the composite map layer which is the output. Figure 1 shows an example of this process. Here, the map was produced through a land suitability analysis model using MADM. The proposed areas to build a resort were selected by assigning weights to different features based on the criteria given by the resort developers.