[cad321]

When you say reletive to the field, are you referring to heading, your xy coordinates, or both? If it is just your heading I would think you'd be ok, however if you're trying to us the navX to track your xy coordinates aswell, you will most likely deal with a substantial amount of drift.

Disclaimer: I have never used the navX board, this response is purely based on what I have read others post here on chief.