Understanding the values making up a Suitability Map

[SteveLynch]

When building a suitability model, you work with different criteria—such as elevation (measured in meters above sea-level), land use (described using text), and distance from roads (measured in miles). Because these criteria use different units and formats, you must first transform them to a common scale to compare and combine them effectively.

Setting Up the Suitability Scale

In the Suitability Modeler  application, you start by defining the range for your suitability scale on the Settings tab. By default, this scale ranges from 1 to 10. This scale helps you express the relative importance of different values within each criterion.

Transforming Criteria

On the Suitability tab, you’ll transform each criterion to fit this common scale:

1. First Criterion Transformation:
• When you transform the first criterion, a new layer is created with values ranging from 1 to 10 (using the default suitability scale).
• The suitability map at this stage is simply a copy of this transformed layer, since only one criterion is included.
2. Adding More Criteria:
• When you transform the second criterion, another layer is created, with values ranging from 1 to 10 (suitability scale), and is added to the suitability map.
• Now, the suitability map’s range expands (for example, from 2 to 20) because it combines the values from both criteria.
• Finally transform and add the third criterion.

Applying Weights

If your criteria have different levels of importance, you can assign weights to them. For example, if all criteria have a weight of 1, they contribute equally. If a criterion is more important, you assign it a higher weight. The transformed layer for each criterion is multiplied by its weight, and the suitability map is the sum of all weighted transformed layers.

Interpreting the Suitability Map

On the final suitability map:

• Low values (shown in red) indicate areas that are less suitable to build a ...
• High values (shown in green) indicate areas that are more suitable to build a ...

This process ensures that all criteria, regardless of their original units or formats, are fairly and consistently compared in your suitability analysis.