I support this idea, and this effort. ;-)
Not a criticism: I recently re-watched the movie, and as I live in the city and know its streets pretty well, I was mapping out the locations in my head as the characters were talking about them. Glancing at the map you've started, my non-expert mind wonders if you've chosen a region that's zoomed-out a little too far? I think most of the action takes place in a small central region of the map, including the finding of Miles Archer's body and Sam Spade's apartment. But I could be wrong. Have you already picked out the points of interest that you're planning to map?