[gnormhurst]

I looked at the data in the spreadsheet. I plotted the dx values and the dy values (I assume these were the result of double integration and represented position). Each seems to have a recognizable trend. If this roughly corresponds to the movements you were applying to the robot (you didn't say), I'd be encouraged that the data could be useful. Sure, it's a little fuzzy. The trick is to filter out the fuzzyness without delaying the data so much that it's no longer useful.

If you need instantaneous location to within an inch, it's probably not going to be useable. But if you just need to know if you are probably past the wall and should turn left, it might work.