Software for DIY off-road navigation

Waypoints, Routes, Tracks

As a basis, you indicate the waypoints for your map on your home PC in QLandkarteGT with help from your favorite map server. From your waypoints, you calculate the routes based on the Open Route Service (Europe only) or MapQuest. From these, you create tracks with altitude data with help from the Geonames.org server. These steps were described in my previous article in the series.

This is where the input comes in, or storage on the USB stick. Unfortunately, the OpenStreetMap project delivers only small map sections in OSM format, not entire countries or continents.

The database for the entire world, planet.osm , for example, takes 32GB of compressed data after unpacking, almost half a hard drive. And, QLandkarteGT can't read OSM maps – only those in uncompressed Garmin format.

As Figure 8 shows, you have three different ways to get to usable maps for the off-road trip. Two of them require loading completed maps, either in Garmin or OSM format. The third takes more work, using Merkaartor to assemble your own OSM map from parts.

Free Maps in Garmin Format

To avoid misunderstanding, the term "Garmin maps" in this article refers to free OSM maps in Garmin format. Inquisitive users have already partially reverse-engineered the undocumented Garmin format [6], as described in some detail on the project website on SourceForge [7].Volunteers are calculating the format from OpenStreetMap sources and providing them for download, thus the material is neither produced nor supported by Garmin itself.

The maps are actually from the OpenStreetMap project, but in Garmin format, and the authors explicitly allow free use of them. Please read the authors' terms of use – some request payment or apply certain restrictions based on payment.

Editing these maps isn't recommended, because it is a hard and tedious task (more on this later). If you still want to modify them based on errors you detect, use Merkaartor together with the OpenStreetMap server (also more on this later).

Your changes will hopefully make it back sometime to the OpenStreetMap map in Garmin format. Critical handling of OpenStreetMap maps is especially needed if you want to traverse unknown or particularly dangerous territory. Additionally, you should bring along a good map from a well-known geographic publishing house and a compass.

The free Garmin format maps are distributed across multiple websites. The OpenStreetMap wiki [8] provides a comprehensive list of these sites. You usually download them as compressed files, with sizes in the gigabyte range, based on the region, country, and continent. Not only does the download take a while, but the unpacking does, too: In my test, a OSM_egeneric took the AMD six-core processor with 8GB RAM almost two minutes to unpack.