I am going to try to add (x,y) coordinates to the spreadsheets as I go through these dungeons - but of course I'm starting on floor 67 of PotD, so there are a lot of floors I'll be missing. My idea goes like this:
Start at the left-most square (maps are diamond-shaped in isometric view, so that makes sense), which will be denoted (1,1). For the x-coordinates, press right on the D-pad; for the y-coordinates, press up. I'm not sure if that's standard, so I'm willing to be corrected if someone has a better argument about how to do this, but I was a math major in college and it makes sense to me that x goes up when you go right and y goes up when you go up.
A nitpick -- Could you start at 0,0? Basically that means that for any x,y you navigate to that corner, then press right x times and press up y times. --- Vladof! You don't need to be a better shot, you just need to shoot more bullets!