Am 04.07.2009 um 10:04 schrieb Toby Speight:
P.S. it would be interesting to see contour regions (as opposed to lines) suitable for elevation shading layers; another idea is to compute slope aspect for a hill shading layer - maybe I'll look into that when I get time...
Actually I've done that already using octave (matrix calculation application, among other uses). I can share the scripts if you like. The problem there is not to generate the data, but to display it in a usable way on the GPS unit. The DEM maps with elevation and hill shading look "Wow" before you try to convert them into an .IMG file. Then they look like crap, because you have nowhere near enough different layers available. There is an article about how to create a bigger number of shadings by dithering: http://www.cgpsmapper.com/download/Creating%20custom%20types%20to%20represen... But even with this method I think the resulting maps look crap, especially if you look at the maps that the GPS units shows if a DEM model for the map is available. So, anybody interested in figuring out the Garmin DEM file format? I would assume that it might not be too complicated if the DEM data is stored in a sampled format like the SRMT data (hopefully not compressed). This could have the added benefit that you might also be able to view the elevation data and use the 3D display mode on the GPS unit. Regards Thilo