I had an old Stack data acquisition unit for my kart. Thing is probably 10 years old or older now. It had an accelerometer in it which it used to derive track maps. This was a long time ago, and it didn't use a gyro or magnetometer, just an accelerometer. The track maps visually looked very accurate, although I can't say exactly how accurate, and to scale they were, but visually it did a very good job. Accelerometer data is very noisy, so if you are just integrating the raw data, I would imagine the results to be awful. You are going to want to use some form of complimentary filter or Kalman filter to integrate to determine your position.