A while ago I noticed that a place name on a map was wrong, and I decided to fix it up using GPSMapEdit. When I did that, the corrected name appeared overlaid with the wrong name--which made me think it had been in there twice to begin with. I exported the file from GPSMapEdit in Polish format, which is a human-readable form, and sure enough, there were identical features, now with two different names. Back in GPSMapEdit I used the command "Remove Object Duplicates", and it found plenty of them.
The file which covers my home in Massachusetts is a good example (94537047.IMG). It has a size of 9.25MB, but if you import it to GPSMapEdit, eliminate the duplicates (68470 of them!) export it and re-compile to an IMG file, it shrinks to 7.51MB. But given how long compilation takes with cGPSmapper, I'm not going to do it for very many files.
I don't want to seem like someone who's ungrateful for free stuff! Having these maps available is what really makes owning a mapping GPS receiver worthwhile, but it seems as though the files do have this excess data. I wonder if the people who create the map files are aware of it.
When you saved the img file as an mp and exported again as an img, did you have any trouble loading the map to your GPSr? I did something similar, I think, but now I can't download the overall SEUSA map anymore. If I put the original img file back, I can download with no problem.
jbcnbama; did you remake the preview images (probably what you need to do)...
I didn't remake the preview files since my changes automatically showed up in mapsource after I dropped the modified file into the directory. I'll try to re-process the preview files with toolkit and let you know what happens. If that works, it's still saves a ton of time building from scratch. Thanks.