What am I missing?

1.22GB of free space will likely let you do map updates internally for the life of your 3597—or at least for a very long time. I've also deleted unneeded voices on mine and your free space is similar to mine. I did add all available English language TTS3 voice files. At about 30MB/voice, the seven TTS3 and extra non-TTS voices do take up space but I wanted the option of having all English language voices on my 3597.

The map is certainly the largest file on your device. The junction view file is sizeable, too. The DEM map and 3D buildings map together are about twice the size of your JCV file. Other biggies are the voice recognition files in the ASR folder. That's about all I see for big files.

Not that I'd do it now, but you can delete the 3D buildings and DEM map to gain over 0.8GB since they're more cosmetic than functional most of the time. The can't be restored through updates so they should be backed up elsewhere if you indeed do want the space and are willing to lose the two features.

More than likely, you can even auto-delete the DEM map file by using GarminMapUpdater for the next map update rather than Garmin Express.

If a SD card is ever needed for a future map update, the SD option will be offered to you by Garmin's software so that going through the manual clone technique for putting a map on the SD card is not essential, but can be used if desired.

The 3597 is almost new and most of the memory is already used. Not to worry - the SD card is in the slot. I plan to run Garmin Express and whenever needed, the map will be put on the SD card. The cloning method should not be needed.

dobs108

I hope that you have a full backup - but if not, then do so as soon as possible. Since you say you see extensions and hidden file - and I assume you are in mass storage mode - it looks like you can do some experiments after the backup.

I prefer the ISO backup but the other works also.
Backing Up Your GPS (Garmin) {G}
Backup Using ISO File {G}

You might want to try a "portable" package like
SpaceSniffer. get it from http://www.portablefreeware.com/index.php?q=spacesniffer&m=

Download the ZIP package and extract to a folder of your choice. Launch SpaceSniffer.exe

The reason I like this package for this particular application is that you are presented with a "Chart" that has "blocks" whose size represents that folder/file's contribution to the total.

The first time I tried it, I was put off by the display. BUT it gives you a quick idea of where space goes - which is exactly what we want for this situation.

For instance, on my 2595, I see that I have several large files. As Craig has pointed out the large .jcv file is a big file - in my case D3191150A.jcv shows as 478.5MB.

Others might want to try SpaceSniffer to see what you find.

I just looked at mine. It shows capacity at 7.54GB, 6.21GB used and 1.33GB free. All of my custom POI reside on a SD card for no particular good reason, just a leftover habit from when I had to on the 750 after the maps no longer fit.

I think there is more under the hood than we can see even in mass storage mode. I guess the answer is there is nothing you're missing and the files you have removed have pretty much freed up as much space as you are going to get. I had good service from the 750 and hope that this 3597 will last well into when it might become necessary to use the SD card.