I haven’t played with my GPS in a couple of years. I keep on getting notices that my maps are old and that I should update them since the one on the system is from around time of Columbus and there have been significant changes. I guess the earth is round or something.

To start, I planned to reinstall my old Garmin PC software, MapSource, which needed the original with serial to install. While I was poking around, I found that there is a new and improved PC-based mapping program from Garmin, BaseMap (free).

I found some free legal GPS maps online. The site, GPSFileDepot, has lots of excellent user-made maps. I picked up a topography map of the state of Colorado. I’m running 64B Win7 and had to install a starter map first.

So, now I have a Colorado Topo Map  on my PC. Now comes the fun stuff. I’m going to save you the long, sad story on the intermediate steps and get right to it.

Disclaimer:  You might break something. You might get hit by a minivan crossing the street while staring at your GPS. There are no guarantees, expressed or implied.  Proceed at your own risk.

HACK #1 – Running a USB Drive as the Nuvi

When the Nuvi is connected to the PC, you get the map in BaseCamp. The problem is that it’s painfully slow. Amazingly, there is a super-simple hack that speeds up things considerably. You will need a 4GB+ USB stick formatted to Fat32.

1. In a text editor, create the file autorun.inf and add these four lines and save:

   [autorun]
   icon=Garmin\nuvi_drive.ico
   action=Garmin FlashDrive
   label=Garmin FlashDrive

2. Put the autorun.inf file in the root directory of the USB drive.
3. Copy the Garmin directory from the Nuvi and put it on the USB drive.
4. Disconnect Nuvi and the USB drive.
5. Plug in the USB drive
6. Run BaseCamp program

Now, BaseCamp should recognize the USB as the Nuvi 265W on the left side pane in the program. Taadah!

An added benefit is that the Nuvi has a limited amount of on-board memory. You can now install up to two additional supplementary maps.

HACK #2 – Installing Additional Maps on Nuvi

You can have up to two supplemental maps on the Nuvi. You need Hack #1 to use this install method. We’re experimenting on the USB drive, not on the actual Nuvi GPS unit. You will need a 4GB+ SD card formatted to Fat32.

Let’s install an additional map, Colorado Topo Map, on the USB drive.

1. Create Colorado Topo Map IMG.

On Menu bar Maps > Install Maps

Select all of the regions by right-clicking outside the map, hold the right-button, and drag to select all regions.

What you are creating is a file called, gmappsupp.img

If the file already exists, it will be over-written, so you’ll get an “Are-you-Sure?” pop-up.

If you have and want to keep this file, copy it to another area, like your Desktop and rename it something descriptive like: jeeptrails_gmapsupp.img

Garmin lumps the original map file into gmapprom.img

The Colorado Topo Map is contained in the file, gmapsupp.img

It’s a good idea to copy and rename the file, cotopo11_gmapsupp.img

2. Prepare and Copy files to SD card.

On the SD card, create a directory, garmin

Copy the cotopo11_gmapsupp.img into the garmin directory on the SD card. Rename the file to gmapsupp.img

If you’d like the jeep trails map, copy the jeeptrails_gmapsupp.img into the garmin directory on the SD card. Rename the file to gmapsup1.img

I read on a forum that the Nuvi 265W (latest firmware) can handle up to 2 supplemental maps.

3. Select Map on Nuvi

After inserting the SD card in the side slot on the Nuvi, select Tools from the first screen (wrench icon), Settings (bigger wrench), Map.

On the bottom, select Map Info and select (check mark) the map you want.

Hack #3 – Replacing the Nuvi Base Road Map with Colorado Topo Map

Fair Warning. I only tried this on the USB stick, not on my actual GPS unit.

Rename gmapprom.img to gmapprom.img.bak (or just copy on to the desktop as NA-Base_gmapprom.img)

Rename  gmapsupp.img to gmapprom.img

That’s it.

Why would you want to do this? There is a project called Open Street Maps (OSM) and there are img files already made for Garmin. Now, if you want full coverage, the img file is 3.5GB. Maybe, instead of using the SD card, the whole base map could be replaced on the GPS unit… Anyway, this is an experiment for another day.

Good luck and happy GPS hacking!