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Section 4: Pedestrian Tracking


Indoor Pedestrian Tracking

Principle of operation: Foot-mounted IMU

Above: IMU mounting Option 1: Side-mount. Can be transferred among different users.

Right: IMU mounting Option 2: In-heel. Protects IMU and adds no external appendix to the foot. Assures firm fit of the IMU.


  • Records and transmits the position of a walking or crawling person.

  • Eliminates effect of accelerometer drift with every step.

  • Uses patent-pending Heuristic Drift Elimination (HDE) algorithm to eliminate effects of MEMS gyros’ sensitivity to linear acceleration and drift.

  • Works with walking/jogging/crawling/skipping forward/backward/sideways/any direction.

  Right: Crawling firefighter during a test of the PDR system by firefighters of the San Miguel Fire District, in June 2010.
  • Average heading errors near zero in walks of unlimited duration!
  • Average position errors <1% of distance traveled in walks > 30 min
  • Average elevation (Z-axis) errors: < 1 m.

Click on picture to open high-resolution version (1 MB)
Trajectory of a 1-hour walk overlaid over a satellite photo (courtesy of Microsoft Virtual Earth) of the University of Michigan’s North Campus.  The 3,900-meter (2.4 miles) long walk led back and forth through seven large, interconnected buildings. Results: Average heading error: 1.8 deg. Final position error: 8.2 m

For detailed experimental results, click here.


  • Above claimed performance attained only inside buildings.

  • Requires 25 seconds of standing still prior to any mission.

Additional features

  • Does not require any user-specific calibration whatsoever.

  • Indifferent to user changing step-length or gait.

  • Indifferent to user walking backward or sideways.

  • Two IMU mounting options: in-boot and side-mount.

  • Temperature control system assures stable IMU temperature under all environmental conditions.

  • Three modes for Z-axis estimates (see Table I).

Table I: The PDR system offers three modes of Z-axis estimates.
Z-axis Mode
Quick Mode
Average errors: <1.0 m. No need for floor height  measurements.
Uses barometer – therefore not compatible with pressurization techniques
Precision Mode
Average errors < 0.2 m.
Requires measurement of floor heights and uses differential barometer
Firefighter mode
Works without barometer.
Average errors: <1.5 m.
Reliability decreases in high risers.
Requires measurement of floor height.