week 4 summary Aurelien Bonnafont
The current GPSs cannot track the real position without prepare the environment with markers or instrument. The NavShoe device can overcome this problem by providing an inertial sensing.
The NavShoe allows to correct the velocity error by applying a zero velocity into an EKF navigation error corrector when a foot is in stance phase. A ZUPT alone looses accuracy because of the heading drift. This heading can be avoided with a much higher performance gyro, a heading correcting measurement from a magnetic compass, or a GPS correction.
The Compass measurement has some difficulty to give accurate results and this is due to the presence of metals in the shoe’s sole. This problem is overcome by a calibration of the sensor before starting. A preprocessed yaw measurement is necessary before each stance phase because the vector magnetic field is insensitive to the magnetic fields inclination.
Outdoor and indoor without any aided experiment provide relatively good results especially concerning the elevation and this can help to localize exactly the person in a building, like a firefighter. To fix the errors we can use a GPS to correct the yaw drift, indeed test with gps are accurate, even if it still some little errors wich can be generated by gps anomalies, but cannot be use inside building. There exist other way to fix it, like using tracker, map correlation techniques, overhead cameras or covariance intersection techniques. A good MR application which require precise head positioning necessit an head tracking with computer vision or hybrid vision and the naveshoe could help with an approximation of the initial position.
NaveShoe cannot replace head tracking in MR system but can be fully implemented to enhance the accuracy of this systems in the future.
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