I have a gps topo map in .img format (one file) and would like to convert it to .gmap format so it can be used in basecamp. It seems like this should be an easy thing to do but nothing I find on a quick google search seems to work. I tried using the javawa GPS tool found online but can't seem to get it to accept an img file...anyone have any experience or ideas with this? Thanks.

Have you tried GMapTool? It may achieve what you are trying to do.

http://www.gmaptool.eu/en/content/gmaptool

I tried using that but the Mac download doesn't seem to have an actual program to install, just some text files. Not sure if I have to use it through terminal? Doesn't seem to be an easy conversion through that anyways, but maybe I am missing something.

Do you know the source of the .img file? I.e. what program created it? I think there are several types of .img files, for example in Mapsource, the vector maps are stored in files with an .img extension.

Unfortunately I don't know the source program, as I got it from somebody off of a flash drive. I can use it on my GPS (Garmin Oregon 600) when I put it directly on the SD card in the correct folder, but just can't figure out how to get it into Basecamp on my mac. It seems there's a way to import it directly from the GPS into basecamp as well, but not sure how to do that as Basecamp doesn't seem to recognize the file from my GPS either.