I would like to make a formula that derives it by its x,y location in the tilemap..unfortunally its aggravating because the tiles are drawn staggered. I haven't been able to convince myself to go and try and figure it out again yet.
I got most of it figured out, a.k.a it works except for a small issue with facades:
( (tile.Location.X + tile.Location.Y) / 2 % tile.numCols ) + (((tile.Location.Y % tile.numRows) + 1 + tile.numCols - ((tile.Location.X + tile.Location.Y) / 2) % tile.numCols) % tile.numRows)*tile.numCols)
I am sure there is a more efficient way of expressing this, but through some weird mental process plus a pen and paper I came up with that. The issue with the facade is that the first part of it ( (tile.Location.X + tile.Location.Y) / 2 % tile.numCols ) which is also used later, is off by a certain number of "tiles." For this to work at dunmir, it would be expressed as ( (tile.Location.X + tile.Location.Y + 40) / 2 % tile.numCols ) because it is off by 20 tiles (20*2 = 40). The internal ix is off by 12 tiles, and there is a repeating row of tile variations at the end of it for some strange reason, however, the algorithim would still make the same picture.
If that all just confused you, don't worry, I just confused myself.