Using Choropleth Mapping

The Peak District sample project included with GenesisIV uses a geological map as a simple example. Load GenesisIV, then open the Peak District project (see the Getting Started tutorial if you don't know how to do this).

Once loaded select Geology from the Chloropleth drop down list above the 2D image. A shaded geological map is shown behind the topographic map - moving the cursor over the 2D window then shows data about the area selected below the image - here our cursor is over Millstone Grit.

In this example we've also set the 3D image to show the topographic map overlay (without height shading) and zoomed in a couple of levels in the 2D image.

Setting up choropleth layers is a straightforward task. We'll take a look at the Geology layer in this example for illustration. Open the Layers Editor by clicking on this button, and select Geology from the layers list. New choropleth layers can be set up by clicking the New button underneath the layers list.

The choropleth layer is simply an image matched with color information. The Hgeol.bmp image used in this case is shown below. Up to 8 colors can be assigned to different properties. To set each property up enter the property data in the text box, and click on the color button besides this to set the color. Unneeded slots should be left as black.

Our choropleth image is a simple bmp file. Note however that it is very important the the property areas are solid blocks of single color - this will probably not be the case if your source image was in jpg format, and in this case the image will need to be cleaned up in a paint program (the posterize filter, if your software has one, tends to be very useful for this).

Your choropleth image must be placed in the overlay directory for the project (as set up in the Project dialog)