Methods and systems for identifying a spatial relationship between a frame of reference associated with an accelerometer mounted in a vehicle and a frame of reference associated with the vehicle Accelerometer data is received from an accelerometer and vehicle data is received from a vehicle network of the vehicle, a long term average of the accelerometer data is used to determine the direction of gravity in the frame of reference of the vehicle. In addition the vehicle date is used to determine changes in speed of the vehicle, and thus to determine the direction of the longitudinal axis of the vehicle in the frame of reference of the vehicle. From these determined directions, the spatial relationship between the frames of reference may be determined.