54 MW810 Mobile Workstation Vehicle Installation Manual
Automatic Calibration
Basics
Automatic Calibration takes place continuously & transparently during periods of good GPS
reception while driving around.
Benefits
• Accuracy improves over time of operation
• Fully compensates effects from aging (aging effects of gyroscope)
• Temperature compensation enables high accuracy at different temperatures
GPS measurements (PVT) are used as calibration references for
Gyroscope turn rate sensor
• Offset(Recognize straight routes)
• Scaling factor(Adjust sharpness of turns)
• Temperature compensation to gyroscope scaling factor and offset
Odometer pulses
• Scaling factor(Relationship between pulse rate and speed)
Installation in a new vehicle
• With a new GPS receiver installed in a new vehicle, the accuracy is only moderately good
until sufficient calibration data has been collected, e.g. during a first drive
• With the time, continuous calibration results in continuous improvement of dead reckoning
accuracy
Small discontinuities
• Small discontinuities, like deviating wheel diameters from exchanging tires (summer vs.
snow tires), will be balanced out by ongoing automatic calibration
Significant changes
• Applicable if the Sensor-based GPS receiver is transferred to a different vehicle or if a
different gyroscope is connected.
• Calibration parameters must be reset. A UBX-message (UBX-CFG-EKF) is available to
invoke th
e reset.
• For optimum navigation performance the new system needs some one-time learning time
and distanc
e for calibrating the various sensors inputs.
• Normally, a good level of calibration is achieved very quickly with a single short road trip
where GPS re
ception is good.
- Odometer pulses are calibrated with driving a distance (scaling factor)
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