Florian and Gert wrote in reply to my appeal:
On Fri, Aug 28, 2009 at 03:45:28PM +0100, Steve Hosgood wrote:
Detectives wanted!
Some or maybe all of the global index is in the .MDR file. All suggestions are welcome, but I don't have cGPSmapper nor a workable copy of MapSource.
So if you guys can try out your ideas and post observations here, or add to the information on the wiki it will all be very welcome. There is some information embedded in Steve Ratcliffe's well-known (and ancient) .java program that partly decodes .mdr files, not all of this is in the wiki yet. Specifically, Ratcliffe seems to have deciphered some way into the MDR10/11 blocks that allegedly contain POI lists and indexes - that stuff isn't on the wiki yet. Someone better than I at reading .java files might do it better and quicker (hint, hint!). I'm a C/C++ programmer myself. Other attack vectors would include decompiling MapSource and/or running it under a debugger to see what it does. To be sure we will expect to be playing "Mastermind" with .MDR files for quite a while I suspect, tweaking known-good Garmin versions and seeing what happens when you try and load Garmin GPS units with the tampered versions. It's all good fun. But seriously - the more the merrier. There's a *lot* of work here. Steve