• Records and transmits the position of a walking person.

• Is based on our PDR system, but optimized for indoor use.

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

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

Features

• 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.

• 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.

Limitations

• 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).