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I've already got one of these in my Garmin directory on my Montana 610.

I'm not so sure about this...

I've read that you can just rename a new gmapsupp.img to gmapsupp1.img or gmapsupp2.img etc. and add it to that same directory.

Is this true? Safe to do?




Also have one in (I) garmin directory on the unit. I think this is City Navigator on the SD card.


Can I add additional gmapsupp.img files without screwing things up, and, if so, where should they go?


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Yes you can rename the map file to anything with a .img extension. By default MapInstall names the file gmapsupp when it creates it (exception apparently the latest MapInstall version uses the name of the map). The  only exception may be .img files on a preloaded microsSD card that is purchased from Garmin. I've never played with those so I can't comment. Also you can create individual map files using Map Install and then rename them to reflect what is in the file (i.e Topo24k West.img for example). Then you can copy the file onto your PC\Mac hard drive. Once you have this file on your hard drive you can copy it onto any SD card in the Garmin folder and it will appear on the gps (except locked maps like City Nav which only show up on the registered gps). You can basically have as many .img files as you want on the card and they will all show on the gps. The one caveat is that the total number of map segments contained in all the files cannot exceed the map segment capacity of the gps. That's 4000 segments for a Montana and  15,000 for a 276Cx. Not sure about other models.The Topo Maps contain a large volume of segments. You can view the number of segments loaded in MapInstall. Alternatively you can use a free utility called Javawa Device Manager to view the map file info.




montana dir.jpg

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Thanks Randy

I'm still playing around with Prescott NF MVUM, trying to get 'em on the Montana. I'm getting closer with your help. Appreciate it.

They are pretty big. I will try some small tests next.

I've got the time right now....

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