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Name of map file on garmin GPS

Started by dessmo, October 11, 2022, 01:57:04 AM

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Hi, I have an Garmin Astro 320 where I am installing new maps from I am downloading the maps for Garmin GPS. After some initial struggling due to the wrong format of the SD card (must be FAT) and name of map file it now works. But I am only able to have one map file working at the gps named gmapsupp.img. So my question, must the file be named like this to work, or is a way around this so I can have more files at the same time. The map file is big and covers the whole country (Norway), but I would like to have more countries on the GPS since I move around an hunt in different countries. I am not using Garmin software like map installer to instal the map, just copying the file onto the SD card and changing the name.


Not familiar with the Astro, but it sounds like an older model. You are correct, these old devices only recognize one file named gmapsupp.img. However, with Garmin's older system, .img files are actually "containers" that can hold multiple maps.

I would suggest using Mapsource and not Basecamp with this old GPS, since that was what it was designed for. Read this tutorial carefully and specifically note step #8 that says:

"Repeat steps 2 through 7 for any other maps you want to load at the same time"

That is the key - you have to select portions of ALL the maps you want before sending them to the GPS. This will cause them to all be bundled into a single gpmapsupp.img file.

However, this part of your post suggests you could have a problem.

"The map file is big and covers the whole country"

Maps are made from smaller "tiles" or "segments" and these old devices are very limited in that respect. They can only accept about 1000 segments total. If you send more, some of the maps will not work properly. Impossible to generalize, because it depends on your specific maps. However, you cannot exceed the segment limit.

I gave up on Garmin awhile ago and no longer have Mapsource installed, but IIRC you will see the total number of segments at the bottom left of the window, underneath the list of tiles you have chosen. Keep an eye on that as you select areas on the map and make sure it does not exceed 1000.

The segment limit has nothing to do with the size of the file, it is completely different. You will probably hit the limit long before the 4gb filesize limit of the FAT32 filesystem.


Thanks Boyd for your answer that makes sense. It is correct that is is an older GPS/dog tracker, but it still works very well. It is very popular within the hunting community due to its simplicity, reliability and no touch screen. I am familiar with Mapsource, but it is a pain in the a.... since I am using a Mac. The map I am installing is already put together of all the segments required to cover the whole country, but not sure how many that is. Will check and see if it is more than 1000. Thanks for your assistance:)


I am also Mac-based, but I heavily use a Windows 10 virtual machine with Parallels. There just aren't enough mapping/GIS apps on MacOS unfortunately.

Give Basecamp a try. Theoretically, Garmin MapInstall will automatically figure out how to properly bundle maps together for your GPS. In reality, I find it pretty confusing and buggy. But if you already have a gmapsupp.img file that you want to use, not sure if MapInstall can do that (it can with newer devices). Would be best to have all the maps installed in Basecamp, then you can choose the parts you want and send them all to the GPS in one bundle.

I don't think Basecamp/Mapinstall shows the number of segments like Mapsource, but I may have just missed that detail.

Also have a look at GMTK and Device Manager from javawa, they are very nice utilities and were available for both Windows and MacOS. However, I believe they broke in some versions of MacOS (Catalina?) a number of years ago. Unfortunately the author suffered a stroke and had to give up maintaining these programs.

Anyway, if they will run on your Mac they may be able to combine maps for you. The device manager program also shows total segments IIRC.


It is nice to see non spam posts being made :)

I downloaded and used imgtool to see how many tiles were in the Norway map and using the map id # it looks to be 338 tiles give or take a few.  Gmaptool will definitely combine the maps but will run into problems if the map id's are the same for different nations maps, but I didn't dig that far yet.  Have you checked the osm on garmin wiki they may have all the countries you're interested in, though from different map authors.  There is always old school, a different card for different mapsets.


Thanks, I will look into that. Appreciate your assistance and knowledge👍🏻