Analysis - IDRISI

We started this project in IDRISI with a 50m DEM of the GVRD.

With this we needed to see where the flat land was. This was done in a series of steps:

Action	Picture: (Click on the picture for a larger detailed image)	Comments
Slope		A slope module was used that calculated the DEM elevation. The results were in percents where 45° equals 100%. The largest value we had was 74.37% which is 33.5°. This is what we are up against on the North Shore.

A soccer field is anywhere from 90m x 45m which is 4050 sq m up to 120m x 90m which is 10,800 sq m. It is best to have a 10m buffer around the field which made the minimum size that I wanted 5000 sq m. I then tried to think of the steepest slope that I have seen held back by retaining walls at fields to determine what was the largest slope that I could approve for a new field.

I initially thought a 20% would do but that is a 9° slope. That means over the 100m length of the soccer field the elevation can change by 15.8m. This was too great for our purposes. I decided upon a 10% figure which is 4.5° or an elevation change of 7.9m. This is still a large slope but I believe if we have no budget constraints it is possible if all other criteria are met.

Reclass 20		This was my starting criteria. It is here to show what a large difference a 10% difference in angle makes.
Reclass 10		This is the result that was used in all future analysis. The potential area is less but more realistic. These two screen shots also show the new window that zooms into only the North Shore.

Once we had all the area on the North Shore that was relatively flat we needed to determine which regions had large enough areas that we could fit full size fields in. Again we are looking at a minimum of 5000 sq m.

Group		Group looks at the individual pixels and determines, by looking at the cells around it, whether it is part of a larger "group" or whether it is all by itself.
Area		Once we had the groups we calculated area in square meters.
Reclass		The resulting areas were those that had an area of greater than 5000 sq m and were part of the flat land scenario from above.

This was the intermediary step that we then converted to ArcGIS for analysis there. One thing that was already becoming apparent was the trend for the flat land to follow creek or river beds up the mountains. This must be looked at in ArcMap. There is still many options for our fields. During the Vector analysis there will be more removed.

The Macro Modeler

This is all the steps from above. This is the easiest way to change criteria without recreating the entire scenario. For example when I decided the slope requirements were too steep it was an easy change in the RECLASS module.

Once we have converted the IDRISI Raster data to be usable in ArcMap we will do more analysis there.

Now onto the Vector Analysis...