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.