Trukk,
Every numbered map that I have encountered was done the way you're quadrant map points out. What I like about the above picture where you actually draw mid lines north / south and east / west, it helps a great deal to imagine the actual field target.
Hotard starting with the spawn hangar (only helps with Vehicle Base maps). I have also found it a lot clearer when assigning Vehicle Hangers at a vbase to assign them by their surroundings. For example "radar hangar" conventional system 1, "spawn hangar" conventional 2, "twin hangar (left/right)" conventional 3 and 4, gives the assigned bomber some visual clues. Other descriptive adjectives commonly used, "big pad, small pad, stand alone, and the newly added Storch hangar".
The best use of the number system gives both hangar number and surrounding clues. Remember there are maps and fields (usually ports) that are not laid out in the same direction as the maps.