MGM Howto

MyTrails 1.1 and later can create offline maps directly on your device, so using an external tool is not required. Of course, the following desktop-based tools offer more flexibility.

Which tool should I use?

If you want to download existing map tiles from the web so you have a local tile cache on your phone, the best tool is MOBAC.

If you have a scan of a paper map, or some other type of picture of a map, then you should use Mapc2Mapc or MapCruncher.

Using MOBAC to create an MGM cache of web maps

There is an issue with the older implementation of MGM in MOBAC which causes some MGM folders to be empty. Please make sure you use an up-to-date version (1.9 final or later).

MOBAC is an open-source Java tool that makes it very easy to generate MGM packs from a large choice of online map providers. It runs on all major desktop operating systems and is actively maintained for new providers and new map formats. Unfortunately, its author has been forced to remove map definitions for all non-free map providers; if you look around a bit, you should be able to find map definitions in the form of XML documents that MOBAC can use.

MOBAC does not run on your Android device, you must have a computer in order to use it and transfer the maps to your device using your USB cable.


MOBAC comes as a zip file, which you should extract to your hard-drive.

Running MOBAC

On Windows, you should double-click the Mobile Atlas Creator.exe icon. On Unix-like platforms (including MacOS X), you can run from a command-line. Or you can double-click the Mobile Atlas Creator.jar file and usually ignore the resulting error message.

Creating the MGM pack

  1. Pick the map you’re interested in from the list of available maps. There is a very large variety of map sources and more are added regularly by the MOBAC team.
  2. Select the zoom levels you’re interested in. Be careful that selecting “deep” (high number) zoom levels dramatically increases the download volume, and the size of the MGM pack you will have to transfer to your device.
    Mobac calculates the number of tiles based on the selected area and zoom level; each tile adds about 25kB, so 40,000 tiles is approximately 1GB.
    Please keep the zoom levels contiguous, or MyTrails may display the map incorrectly or blur the available tiles.
  3. Select the area on the map you wish MOBAC to download.
  4. Pick a name for the layer and click Add selection.
    You can do this several times, and change the map source each time. This will create several MGM packs that you can store in the same directory on your device.
  5. Select the MyTrails format (MGMaps/MyTrails (MGM)).
  6. Click Create atlas. MOBAC will download the relevant tiles and generate the MGM pack. This may take a long time.

Using Mapc2Mapc to georeference a scanned map

  • Download Mapc2Mapc, a shareware Windows application that allows you to align a scanned, stitched or photographed map to existing maps coordinates (a process called georeferencing).
  • Mapc2Mapc is able to directly output MGM packs, so no other software is required. Extensive documentation is available, including step-by-step how-tos.

How to use:

  1. download the script to Win XP (other versions of Windows may also work)
  2. install and buy mapc2mapc ( version >= 485
  3. edit the script to define the variables (lines starting with SET)
  4. drag and drop map files (for example .map) on the mapc2mytrails.bat icon (10 maps maximum)
    or drag and drop a folder containing the map files

New maps can be added to a folder that already contains MGM files, the maps will then be merged.

Using MapCruncher to georeference a scanned map

  • MapCruncher is a free Microsoft tool (Windows-only) that allows you to align a scanned, stitched or photographed map to existing maps coordinates (a process called georeferencing).
    MapCruncher is no longer being maintained, and is no longer available on Microsoft’s web site. I am hosting a backup on Dropbox.
  • MapAlive should be used to generate an MGM pack from the tiles generated by MapCruncher; 64 tiles per file is the recommended setting for 1,000 to 1,000,000 tiles.