I've had some trouble with sensor drift in INS mode. Even while the IMU is stationary it would drift up to 20 meters. I thought it might be the GPS (it is a fairly cheap U-Blox GPS outputting NMEA) but even when I hardcoded the GPS lat/long/alt values so they were perfectly consistent the IMU would still drift up to 12 meters while stationary.

Does anyone know if this is just a limitation of the sensor or if there are some configuration settings I can tweak to improve this?