route outline

  • tracking is possible with and without a paired mobile device

data recording

  • sampled data is saved to a micro SD card and if connected transfered to a paired mobile device

data transfer

  • the position is received in realtime during the tracking session via the bluetooth interface

9-axis sensor

  • Accelero-, Gyro- und Magnetometer
  • I┬▓C Interface for communication with the ┬ÁController
  • during the initialisation the accelerometer and gyroskop Biases are calibrated
  • 64 Hz interrogation frequency


AHRS-algorithm from Sebastian Madgwick

  • orientation is relativ to the earth
  • X-axis points north
  • Y-axis points west
  • Z-axis lies along the gravitation axis
Magic aka Madgwick Algo.

sensor fusion

  • combining data from different sensors
  • into new and precise measured data and results
  • Madgwick: main orientation achieved via the gyroskop, accelerometer and magnetometer compensate its drawbacks


  • individual speedups towards north, east and vertical
  • the visited path is calculated with a double integral
  • saved velocity is zeroed out with every new step
  • orientation correction happens only in stationary mode