I did some testing of relief contours generation before the official release of GroundTruth v1.3. I generated 10m interval contours for area of Slovenia and its neighboring regions, and here are some numbers:

  • Area: minlat:45, minlng:13, maxlat:47, maxlng:17
  • IBF file size: 28 MB (IBF file contains contours information in a binary form). My estimate is that the equivalent Srtm2Osm-generated OSM XML file would be at least 350 MB large.
  • Time taken to generate Garmin IMG files from IBF file: 15 minutes on my machine
  • Total size of generated IMG files: 53 MB
  • Total IMG files count: 125 files

As you can see from the first screenshot below, the contour files are split into a 15′ grid. You can therefore choose which of the tiles you want to upload to your GPS unit.

I had some problems with cgpsmapper reporting “Too Big RGN Table Structure” error for grid cells with a lot of contours. To overcome this, I reduced the cgpsmapper’s TreSize setting from 4000 to 2500 and then it worked without problems.

I’ll also try to experiment with the SimplifyLevel setting (currently no simplification is used) in order to reduce IMG file sizes and (possibly) rendering speed on GPS units.

All in all, I’m very pleased with results. I hope to be able to release the new version real soon!

GroundTruth ContoursGroundTruth Relief Contours

GroundTruth Relief Contours