1. Improvements on a Novel Hybrid Tracking System
Markus Zank; Leyla Kern; Andreas Kunz
ETH Zurich

2. Content Background and application field
Classification of tracking systems
Basic operation principle
Building and testing the system
Conclusions and outlook
11/29/2018

3. Background and application field
VR environments gain immersion by the sensation of real walking on ground (without treadmills)
Sizes and distances can be perceived more naturally than with a “flythrough” (using a joystick, etc.)
Requires continuous accurate tracking even under adverse conditions
Hybrid systems (optical and inertia-based) often not sufficient due to drift
11/29/2018

4. Classification of tracking systems
11/29/2018

5. Classification of tracking systems
Inertia-based systems drift quadratically with time:
Errors occur even if the user does not walk
Frequent recalibration necessary
Electromagnetic tracking systems directly measure distances
Need fixed reference point
Not suitable for exploring large virtual environments
Do not drift with time
Error increases with large tracking distance
11/29/2018

6. Basic operation principle
Idea of a “quasistatic” reference on the stationary foot
Base station is attached to HMD, measures distance to stationary and moving foot
Distance from one foot to the other can be calculated
Error linearly accumulates with the number of steps, but not with distance or time
IMU is used for step detection only
11/29/2018

7. Basic operation principle
Old switching mode changed reference one a foot entered the swing mode
Large position error since reference is switched during swing phase
New switching method changes reference once a foot enters stance phase
Small error since reference is switched while both feet are in stance phase
11/29/2018

8. Building and testing the system
Razer Hydra electromagnetic tracking system:
Two sensors, one base station (cable-bound)
Two ReSense accelerometers (Blue tooth connectivity)
Razer sensors are attached to shoes’ heels
Accelerometers are attached to shoes heels
Razer base station is attached to head-mounted display
11/29/2018

9. Building and testing the system
Old and new system setup is compared
In both cases: Oscillations stem from walking
Reference is taken with an absolute optical tracking system Intersense IS-1200
Old setup immediately shows measurement error
New setup follows ideal path for about 14 s (slow walking)
11/29/2018

10. Conclusions and outlook
Proposed system is able to bridge situations with invisible markers
Recalibration is less frequently required than for inertia systems  larger distance of markers possible
Electromagnetic system still cable-bound, wireless preferred  STEM
Sensor signals will also be used to control limbs’ movements of an avatar
Foot’s roll motion is still a source of error  will be eliminated in future work.
11/29/2018

11. Thank you for your attention.
{zank,
Thank you for your attention.