Thanks for your interesting explanations. I had already the same idea, but not the time yet to do something.
I can't imagine, that the coordinates are relative coords. I think they are in somehow format, that must be possible to translate to any usable format.
Could you post here an part of these data?
I also think, it must be possible, to make a gpx file with all trails from this SQL files. From such gpx it is easily possible to make a .gpi-file or a transparent layer in .img format.