Questions about map update (do new updates erase previous map data?)

It cleans up after itself, internally. On the SD card, it overwrites what it puts there. It's only map files.

If internal memory gets used up then uses sd card what happens when sd card gets full? My unit has a 32gb sd card limit. it seems that old maps should be erased so memory isn't used up. Maybe I am mis-understanding how it works.

I'm not in full agreement with Phranc. I have a 3790lmt which like you ran out of room. I allowed it to do the update on the sd card. It did not clean up after itself. There were files left behind and i went behind and deleted them. I don't do it that way anymore i use this method http://www.poi-factory.com/node/39231. It works every time and no files left behind. You won't run out of room with the sd card. The map size doesn't increase that much but it doesn't matter if you update using the link i gave you. You can easily use another sd card later.

Provided you use Express and it puts the map files there it will delete the previous ones, and with even a 16Gb card you won't have any issues, so your 32Gb will be fine

I have two nuvi 3579's which have required the SD card on the last several map updates. The only thing Express has put on the SD cards so far is the JCV file. It has continued to put the map files and all other feature files in internal memory. And it has cleaned up the previous map version files correctly.

I found the same, only the JCV file goes to the SD.

If there's space on the device for the map files then it will just move the jcv file, otherwise it'll be the map files.

gmappupdate.gsd (30 bytes) Gets move to the Garmin folder on mine, plus the JVC. I want to say, it needs the space to expand the maps for installation on the SD because the internal memory does not have enough space. The JVC is only 511mb and there is sufficient memory on the unit for it,

https://forums.garmin.com/apps-software/mac-windows-software...

Garmin Express leaves quite a bit of "stuff" on your PC as well. Typically the "old" maps (on the PC) are about 6 to 7 GB in size. I only keep two, the current that is installed on my devices, and the map immediately prior to that.

I cant find anything that is using 7gb in my internal memory.
There are no map files on the 2557 at all. Cant figure out how it been working all these years...lol

They're there but you have some hoops to jump through to see them. Your 2557 probably needs to go from MTP mode to MS mode. Then if using a PC, there are several Windows folder settings that need to be just right. If you want to see the big files, start here:

http://www.poi-factory.com/garmin/problemsolver#system-folde...

Once you can view the .system folder and sub-folders, you will find many big files.

Ok I got it in MS mode and there is a system folder with 6.4 gb of files. one file gmapprom.img 3.4 gb. still cant find the other 4gb. Can I leave the setting in MS mode or do I have set it back to MTP mode?

That was quick. Good work.

You can leave the GPS in MTP or MS mode. I think several of us here leave our devices in MS mode. I think some GPS models even offer both a 'MS One-Time' mode or a 'MS-until you turn it back to MTP' mode.

Besides the big map file, other large files are the JCV file, and if your device has these folders, look for big files in .system's ASR and SID folders. The newer higher end devices probably offer more bells and whistles which require big files while some of the older and low-mid priced GPS models may have fewer total GB of files due to some feature(s) not being present. The nuvi 3597 also has an additional map of North America (besides City Navigator) that offers shaded relief to reflect topography which is interesting if you're driving along the South Rim of the Grand Canyon or driving through narrow deep valleys.

I think I'm going to leave well enough alone. my 16gb card should last along time. Thanks every one for the help.

Thanks again
Bob.W

I keep finding map license keys from the previous map on both the 3597 and the Nuvi 660 as well as the on the 660's SD card after map updates. Easy to delete though, going by the timestamp on the files.

Also, GE (& MapInstall) leave the previous map(s) on the PC - if you also install to computer. I do an install to both the 3597 and the computer using GE. Then I use MapInstall to load the map to the 660. Since the map is already on the PC, MapInstall only gets the 660's license keys from Garmin and installs the map (in 2 sections) from the PC. I don't have to D/L the whole map again, so it saves some time.