I’m hoping somebody can confirm a couple of things for me before I actually take the leap and add new maps. Pardon my silliness but I like my new Nuvi 255 a lot and I don’t want to brick it.
Here’s the scoop: The Nuvi came with City Navigator for North America preinstalled. I don’t have the CN-NA on any media other than having taken a full backup of the flash as a disk drive. I would like to add the OSM maps for Benelux from http://emexes.powweb.com/osm/download.html. I’ve downloaded the maps I want, hack-installed MapSource, and am ready to hit that “send to device” button…
… and then I chickened out.
Here’s what I want to know:
Will I be overwriting the CN-NA maps by doing this upload? The MapSource software reports that CN-NA is “not installed” so I’m wondering whether the software is going to take its actual existence into consideration in the upload. Since North America is the primary place where this device will be used, that would be bad.
Will adding these maps void the warranty, cause problems installing map updates, or give any other such grief down the road?
I was nervous about this also, since I had seen some comments about MapSource wiping out the basemaps on some Garmin GPS. The solution to my nervousness was to install the new maps onto an SD card:
–Verify that your Nuvi 255 has an SD card slot (I believe it does)
–Acquire an SD card. 512MB or 1GB would be enough to cover most of Europe; and are quite inexpensive.
–Insert the SD card, connect Nuvi 255 by USB to your computer, turn on the Nuvi.
–Now when you hit the “send to device” button in Mapsource, you will be given a choice of sending the map to the Nuvi or to the SD card. Choose the SD card.
–The map will be installed on the SD card as a file called “gmapsupp.img”
I have done this a few times with my Nuvi 360, did not have any problems. Any time I connect the Nuvi to internet to check for updates, I remove the SD card first.
This post represents my experience, of course I cannot guarantee your results.
As you already made a backup of all the files, you could just go ahead with your experiments.
The Garmins have their maps organized internally in a (very small) number of files with a name pattern of “gmap*.img”. You probably have two of these files called gmapbmap.img containing the base map and a very large gmapprom.img with the detailed maps. If you send additional maps to the Garmin, MapSource creates/overwrites an extra file called gmapsupp.img. The preinstalled maps will not be overwritten this way, but each time you change your selection of custom maps, you again have to select all of them.
As mentioned by xixi, there is another slot for one gmapsupp.img on an SD-Card. I understand from other posts that the internal memory on Garmins typically is just large enough to hold the preloaded maps. Therefore I would advise that you get the largest SD-Card that is supported by your nuvi (or that you can afford). CN Europe does not fit into 1GB so 2GB is the recommended minimum; your nuvi 255 probably accepts even larger cards but I have no experience with that.