If your stuck with JPEG or GIF file, you may want to try to this method:

In the terrain editor with your terrain already loaded from the picture:

1. Select the filter altitude button (top right of the editor window).
2. Right click on the filter and select 'load filter'.
3. From 'Saturation' category, select 'Step 50%', or 'Step 70%'. There are several Step filters. Select the one that preserves the greys from your picture.

Step filters leave only two altitudes on the terrain.

Charles

Charles