Raster overlays=
Captured images from Google Earth (JPG format),
acompanied by a text file that defines the upper left corner and the lower right corner of the image. Also in this text file are scaling notes and pixel resolution. The text file (plane ascii format) must have the same name as the image file, but will have a "SAT" extension.
The following is an example of one on my TT (go ahead and cut and paste this into a simple text editor and save as plain acsii text. Don't forget to rename it as santa-barbara.sat). Copy that file into your tomtom into the "raster" folder.
The file name is "santa-barbara.sat"
-
-120.398740
34.954341
-119.316285
34.377242
150
1500
1024
666
The image that goes with it is at this link (go ahead and down load it and put it into your tomtom in the "raster" folder. The file name should be "santa-barbara.jpg"
http://s36.photobucket.com/albums/e5/RandyTrent/Tomtom/?action=view¤t=santa-barbara.jpg
(I hope that image did not get screwed up by photobucket. Sometimes it reduces the file size with out me knowing,, it should be 1024 x 666 pixels)
Once that is done you can fire up your TT and go to the browse map feature (make sure the image feature is on). Scroll over to santa barbara, California (or navigate to the 93111 zip code if that is easier for you) and start zooming in. You will be able to tell when this map takes over the screen image. The TT will still put it's version of the roads in, but the background graphics are all from what you just installed. Keep in mind that this is a wide area view and will not have super detailed high zoom resolution. I add more detailed overlays on top of this one (typically at 500~700 feet eye elevation), for all of the cache sites that are not near roads. It is a lot of work, but it is worth it in my oppinion.
3rd party software:
I use "offroad" written by the same guy (and downloaded from the same place) as Tripmaster.
It works a little smother than "browse map" because the maps scroll along as the position cursor moves off the screen. You do not get to do dynamic zooming (that is set in the configuration file that you create within the offroad folder,, again a plain ascii text file called config.map). The text file is quite different than the one that works from browse map, but the principle is the same. also the images that are captured must be in BMP format. Again, a lot of work, but it is a lot cheeper that buying a dedicated hand held nav unit, and paying for a divorce because you are spending all the rent money on toys!
Hope this helps. There are a ton of guys on this forum that know about all this file manipulation far better than me. Maybe one or two of them will help exlpain what I just tried to convey?