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Multiple maps on the same microSD card


I recently purchased a set of GPS maps on a microSD card from a company that sells Garmin-compatible hiking maps. (I use a Garmin Oregon 600.) On the 4-gig card is a single folder named “GARMIN,” which contains the following files: a small file named ‘201506181138340.gma’; a very large file named ‘GMAPSUPP.IMG’; a small file named ‘GMAPSUPP.UNL’; and a folder named “POI,” which contains a single file with the extension ‘gpi’. I understand that UNL and GMA files have to do with copy protection and the IMG file is the map.

Everything on the card takes up roughly 250 megs, which leaves me with about 3.75 gigs of free space.

What I would like to know is: Can I copy everything from the microSD card onto my desktop and then copy those files onto the 32-gig microSD card that holds my other GPS maps so I don’t have to swap out cards all the time? If this is possible, can I simply put the “GARMIN” folder (renamed) on that 32-gig card and the GPS receiver will see and be able to use the maps within?

The 32-gig card’s “GARMIN” folder contains three files: gmapsupp.gma, gmapsupp.IMG, and gmapsupp.unl.

Clearly, the img and unl files have identical names. If I change these file names (to something like GMAPSUPP2.IMG), will the GPS receiver be able to find that data?

Any clarification of how to proceed with putting multiple maps on the same card much appreciated.



  • Boyd 1999 Points
    edited September 2015
    It is impossible to answer your question without more knowledge of the specific map you purchased. Some maps are copy protected in a way such that they can only be used on the original SD card.

    As a generic question, maps can be installed on any card or internal memory and be compatible with your GPS. There is no need to change the file names. The "GMAPSUPP" business is ancient history now on Garmin devices. Older models would only recognize maps with that filename. All Garmin units manufactured since around 2009 (IIRC) will recognize any valid map as long as the file has the .img extension.

    But some authors continue to use the generic GMAPSUPP.IMG name so their products will be compatible with older devices. Also, if you use Mapsource (Garmin's older software) to send a map to a card it will always be named GMAPSUPP.IMG. This also causes any maps you previously sent to be overwritten.

    You could could probably change the names of those three files to something else, but there is no reason why they can't coexist since the two maps already have different filenames.

    Maps must be in a folder named Garmin at the root level of either a memory card or internal memory on handheld devices such as yours. FWIW, on the Nuvi, the maps must be in a folder named Map instead.

    The map itself is the .img file. The .gma and .unl files are used for copy protection and are optional (they are not used for maps that aren't copy protected).

    Since you purchased the map on a card, I'd say the chances are good that it will only work on the original card. Many third party authors use this system. But there is no harm in trying. If it doesn't work, you will have to contact the vendor for help.

    The .gpi file is not a map, it contains POIs. These will appear when you do a search and may appear on the screen depending on what options you choose in the map setup.

    Also, you must format the card as FAT32 or it will not work in the GPS.
  • Thanks for the bad news! Better to know than not to know, eh?
  • Boyd 1999 Points
    Did you try copying the files? Did it not work? If so, you should contact the company that sold you the map, maybe they can provide it in another format.

    For Garmin's own products, they offer maps as downloads, DVDs or pre-loaded cards. The maps on preloaded cards will not work on another card. But the DVD and download versions will work on any card or internal memory. However they use a form of copy protection to lock these maps to the original GPS itself. I think this is a proprietary system that may not be available to third party vendors, which is why they like to use copy protected cards.
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