NOTE: This article has been updated and added as a FAQ. Please refer to the updated article here:
FAQ: Garmin Maps | Cloning Method: Install a Map Update Directly to the SD Card.
I posted this over on the GPS Review forum and thought it might be useful to the POI Factory members. This technique was suggested by member Boyd on that forum. I took his idea and tested it with my two nuvis (755T and 855).
You may have already noticed a certain peculiarity in Garmin software. If you have a removable drive on your computer (SD card or thumb drive) and create a \Garmin folder at the root of this drive, then copy the file GarminDevice.xml from your nuvi into this folder, the Garmin programs like POI Loader and my.Garmin.com seem to recognize the removable drive as a nuvi. Boyd speculated that you might be able to use this quirk to fool the map update installer and directly install a map update to a SD card.
It took some experimentation and several tries, but I was able to install the complete map on SD with both of my nuvis. Both nuvis operate correctly with ALL of the NA map data on the SD card. Here is a summary of the steps I used to install maps directly to the SD card:
1) Do a complete backup of your nuvi BEFORE you attempt this procedure. This MAY allow you to recover your nuvi if something goes wrong.
2) Use WebUpdater to make sure you have the latest software on your nuvi before you try this. If you have old software, you will have trouble with the map download because my.Garmin.com will try to do a software update on your (fake nuvi) SD card prior to the map download!
3) Start with a clean SD card in your computer or SD card reader. Make sure it is formatted FAT32. Create the \Garmin folder. Connect your nuvi to the computer in data mode and copy file GarminDevice.xml from the \Garmin folder on the nuvi into the \Garmin folder on the SD card. [Nuvi 8xx series only: Copy the complete ASR folder and its contents from the \Garmin folder on the nuvi into the \Garmin folder of the SD card.]
4) Safely remove the nuvi from the computer, but leave the SD card mounted on the computer. Log into my.Garmin.com. To verify that the SD card is recognized as your nuvi, go to the myDashboard tab and click on "Scan for devices". Your SD card should show up as your nuvi model in the drop down box. (Note: If you didn't remove your real nuvi from the computer as suggested, it will appear twice in the drop down box ... once for the real nuvi and once for your fake nuvi SD card. You won't be able to tell which is which!)
5) On myGarmin, click on the myMaps tab, select the map download link and use option 2 (Map update installer). Proceed to download and install the map files to the SD card. When the map update installer completes, all new map files are on the SD card in the \Garmin folder: gmapprom.img, gmapprom.gma, gmapprom.unl. On some models you will also have files gmaptz.img, gmap3D.img and DnnnnnnnA.JCV (in the \Garmin\JCV folder). Make sure all files are sucessfully downloaded to the SD card before continuing.
6) If your nuvi supports Junction View, this would be a good time to check the DnnnnnnnA.JCV file that was downloaded to the SD card. If you got the small file and want the large one, you may as well replace it now. Use the link provided elsewhere in the forum to download the large JCV file and copy it to the SD card in the \Garmin\JCV folder. Delete the small JCV file that was downloaded by the map update installer.
7) Connect the nuvi to the PC in data mode and delete the following files from the \Garmin folder on the nuvi internal drive: gmapprom.img, gmapprom.gma, and gmapprom.unl. Also delete file GMAP3D.img and the complete \JCV folder and its contents if they are present on your nuvi. [Nuvi 8xx series only: Delete the ASR folder and its contents from the \Garmin folder of your nuvi.]
8) If present, copy file gmaptz.img from the SD card back into the \Garmin folder of the nuvi. [Nuvi 8xx series only: Copy the entire updated ASR folder and its contents from the SD card back into the \Garmin folder of the nuvi.]
9) On the SD card rename the following files gmapprom.img to gmapsupp.img, gmapprom.gma to gmapsupp.gma and gmapprom.unl to gmapsupp.unl. Delete file GarminDevice.xml from the SD card, so it will no longer show up as a fake nuvi in Garmin software.
10) Safely remove the SD card and nuvi from the computer. Install the SD card in the nuvi.
11) Boot the nuvi, go to Tools > Settings > map > map info and make sure the full NA map (and 3D map if your model supports it) show up and are checked.
12) Test the nuvi to make sure all map detail is working.
On the 755T, the detail NA maps, 3D map, and JCV file all work correctly from the SD card. The only file from the map download that has to be on the internal drive is the gmaptz.img time zone file. After completing this procedure with CN NA 2012.30, I had 3.5 GB of free space on the 755T's 4 GB internal drive.
On the 855, the speech recognition files are updated as part of the map update. The easiest way I found to handle this was to copy the ASR folder to the SD card, perform the map install, then copy the updated ASR folder back to the nuvi. These steps are included in the above procedure.
This procedure worked well for me, but be aware that you are removing your detail map files from the internal storage of your nuvi. TRY IT AT YOUR OWN RISK! Note that these steps are for the older 7x5 and 8x5 nuvis that do not have the hidden .system folder and enhanced map naming features. It seems likely that the procedure can be easily adapted to the other nuvi models of this generation like the 2xx, 7xx and 8xx. I am not sure what additional considerations there are for the newer 1xxx, 2xxx and 3xxx models that have the .system folder. If anyone tries this, please post your results here.

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Very intersting. Thanks for the clear and detailed post.
...
You've put it together very well. This should be put in the FAQ!
Michael -- Nuvi 755T
My friend, you deserve a medal for this !
I'm sure the Powers That Be over at POI Factory will agree ?
Ain't nuthin' never just right to do the things you wanna do when you wanna do them, so you best just go ahead and do them anyway ! (Rancid Crabtree, from Pat F McManus fame)
,
Thanks for the detailed information and spending all the time working it all out for everyone.
Thanks for this useful
Thanks for this useful information.
Kenneth Forde
Some caution
While this will work in most cases, I would advise some caution as SD cards can go bad or if you bought some fake SD cards, it might not work optimally though.
Excellent write up alandb ... I thought Garmin had disabled this method when I tried doing this with the JCV fiasco couple of releases ago, but it works now!
Installing to nuvi 855.
I spent some time today trying this with my nuvi 855. In general the procedure worked the same way as it did on the 755T. But I did run into one issue. In addition to maps, the map update installed some updated speech recognition files in the \Garmin\ASR folder. I found the best way to handle this was to copy the ASR folder to the SD card, update the maps, then copy the updated ASR folder back to the nuvi. I have included these additional steps in the original document.
Alan - Nuvi 855, Oregon 550T, Nuvi 755T, Lowrance Endura Sierra
Thanks
Thanks for sharing this useful info.
nuvi 2460LMT
kewl
kewl
1490t
I am not sure what additional considerations there are for the newer 1xxx, 2xxx and 3xxx models that have the .system folder. If anyone tries this, please post your results here.
I successfully used your procedures on my unit. This freed up my unit memory for the large JCV file. Not all file names appeared on my unit.
I have a problem with my older XP. It will not read the MiniSd card in the (F:) drive slot , so I have to leave it in the Garmin. Then it will read the Removable Disk (K:)
1490LMT 1450LMT 295w Explorist 600
Time zone file.
I just noticed on my 755T that the timezone file (gmaptz.img) was not showing up on the diagnostics inventory screen. The time zones and time function seemed to be working correctly with the file on the SD card. But to be safe I moved the file from the SD card back to the nuvi. It now shows up on the diagnostics screen.
I modified the original document to reflect this change.
Alan - Nuvi 855, Oregon 550T, Nuvi 755T, Lowrance Endura Sierra
Alandb
I tried it again and successfully this time. I have the large JCV file and all 50 states plus Canada & Mexico & the Bahamas.
Thanks
1490LMT 1450LMT 295w Explorist 600
Use the SD adapter
It will not read the MiniSd card in the (F:) drive slot , so I have to leave it in the Garmin. Then it will read the Removable Disk (K:)
Also, make sure you have the latest OS updates from MS. My XP Pro has no problem reading the card.
Unless you have a non-legal version of XP...
nüvi 3790T | nüvi 775T | Those who make peaceful revolution impossible, will make violent revolution inevitable ~ JFK
XP was preloaded on this computer.
I'm using XP media center version, version 2002 with service pack 3. BTW, my older HDTV will not read the Micro SD card either. I have no problem with SD cards.
I do use the adapter
1490LMT 1450LMT 295w Explorist 600
Sounds like the card reader(s) then
Have you tried a different (newer) one?
nüvi 3790T | nüvi 775T | Those who make peaceful revolution impossible, will make violent revolution inevitable ~ JFK
One other thing...
I bought a SanDisk 4 gig micro card , and adapter yesterday, and it wouldn't read, or format. I swapped the adapter to an older one and it worked.
May work for you as well!
nüvi 3790T | nüvi 775T | Those who make peaceful revolution impossible, will make violent revolution inevitable ~ JFK
AH HAH
I have a USB flash drive that accepts the MicroSD/SD adapter. It works with all my microSD cards.
1490LMT 1450LMT 295w Explorist 600
SD map folder.
Spokybob, did you do this install for your 1490T or the 295W? If it was your 1490T, what folder on the SD card did the Garmin map update installer put the maps in? Did you leave them in that location or move them to a different folder? Did you rename the installed maps from gmapprom.* to gmapsupp.* as suggested in the procedure?
Alan - Nuvi 855, Oregon 550T, Nuvi 755T, Lowrance Endura Sierra
Tried it on the 1390T also Now a Brick.....
I was able to install the maps from the site onto the SD card Deleted the files from the 1390T HIDDEN .System folder and now I have a brick, does not see any maps. I can fix this just dicouraged that it doesn't see the files. I renamed them to supp and it still does not see them, looks great for disk space not so great for functionality.
Any Ideas anyone??????
Garmin 3790 LMT - Always on the road around the US.
My 1490t
Spokybob, did you do this install for your 1490T or the 295W? If it was your 1490T, what folder on the SD card did the Garmin map update installer put the maps in? Did you leave them in that location or move them to a different folder? Did you rename the installed maps from gmapprom.* to gmapsupp.* as suggested in the procedure?
I don't remember each & every step that I employed. I did rename the gmapprom.img to gmappsupp.img.
I have 4 folders on the card
.System (15.8MB)\gupdate and locales
Garmin(2.15GB)\JCV folder & the ****.gma and gmapsupp.img
Map(1.35GB)\ the ****.gma and gmapsupp.img
Voice(15.5MB) \ English_American_Jill.vpm
1490LMT 1450LMT 295w Explorist 600
1xxx maps on SD
TMan65, sorry to hear that this didn't work for you. I don't have access to a nuvi 1xxx series with lifetime maps. I wish I did so I could help you figure it out. I suspect the problem has to do with the folder/file names on the SD. What folders did the map installer create on your SD card? What files were downloaded to each folder?
Just going by spokybob's post, it looks like you might need to rename the map files from gmapprom.*** to gmapsupp.***, then move them into a \MAP folder, or perhaps \Garmin.
Alan - Nuvi 855, Oregon 550T, Nuvi 755T, Lowrance Endura Sierra
This is what I saw
I took the Garmin folder copied to the SD card.
No Garmin just SD card now.
Ran the latest Lifetime Map updater tool, it asked if I wanted to reinstall maps I said yes.
It created a Hidden .System folder and made 4 new files same files that were on the original Internal .System folder gmapprom.gma, gmapprom.img, gmapprom.unl and GMAPTZ.IMG. It also Made a /JVC folder in .System (.system/jvc) and put the newest Junction view file there D3153040A.JCV.
Map folder is Blank on original drive.
No map folder nothing else.
So now that I deleted these files from my garmin memory I have NO map version at all and no map detail.
So I plugged it back in (garmin that is) and reran Update to the garmin again and now with a Full internal memory card the maps are back with full detail, and data about the maps now appear again on the system info tabs (before when on the SD card they were all blanked out)
When I check Map Info now I have CN North America NT 2012.30 US& Canada again, I can see the roads again and it looks like a garmin again.
So it doesn't like something but I am not sure what it doesn't like????
I wonder if the unit would boot if I move all files to the 8 gig SD card?
Garmin 3790 LMT - Always on the road around the US.
Why not?
It should boot, no reason not to. Just name the card the same, and copy the files.
nüvi 3790T | nüvi 775T | Those who make peaceful revolution impossible, will make violent revolution inevitable ~ JFK
Awesome tutorial
Worked like a charm for my nuvi 350 and 650. The only thing I did differently was rename the files on the device instead of deleting them (renamed them old-* for all).
A good check is to make sure the device is pulling the mas from the card. Eject the SD card at the "Tools > Settings > map > map info" area and you'll see it disappear. Re-insert the SD card and after a few moments it should re-appear. Boom.
Great write up.
Garmin 1350 lmt - using this method to install to SD
Wow ... after hours of failure using Garmin Lifetime Updater to update Garmin 1350lmt with SD card to full 49 states + Canada 2013.20 ... alandb's method worked.
For the 1350 there are some DIFFERENT PROTOCOLS.
The files deleted from and copied to the Nuvi 1350 are in the /.system folder (not the Garmin folder).
Using Lifetime Updater to install directly to the SD card, a folder SD/.system and a folder SD/Garmin are created.
I moved the Gmapprom files on the SD card from the SD/.system folder to the SD/Garmin folder and renamed them to Gmapsupp. The SD card also has to have a :/Map folder created (empty). The SD:/system folder can then be deleted.
Thanks alandb you're work is much appreciated !
Cloning method for map install
supe97, I am glad you were able to adapt the cloning method for map install to SD card to the 1xxx nuvi series. I don't have one of the newer nuvi models with the hidden .system folder to test with, so I was not sure if the method worked on the newer nuvi's.
I am guessing the map files could have been copied to the \map folder and named anything you want with the corect extensions ... not sure they needed to go in \garmin as gmapsupp on these units.
Alan - Nuvi 855, Oregon 550T, Nuvi 755T, Lowrance Endura Sierra
Thanks for this Great
Thanks for this Great information
Montana 650,62S,1450,Etrex Venture Hc
1350lmt SD card map configs
alandb
You're right on both counts. The map can be in the SD/Map folder and it can have a personalized name.
Going further, I tested the ability of the 1350 to use more than one map from the SD card. I was using three different regions of the 2013.20 North American map as three different maps.
I could only get the 1350 to recognize one of the two SD maps along with a map in the NUVI. This agrees with other users findings in other forums.
I'm very happy with the unit now, thanks to you.
Interesting option. I was
Interesting option. I was trying to install Europe maps to the sd card on my 3490LMT with my North America maps still in the Nuvi.