DR + GPS
STARTER KIT REFERENCE MANUAL
Lassen DR + GPS Reference Manual 122
No Tacho data when GPS is detecting movement
Condition cause: Tacho is disconnected or malfunctioning.
Effect before Action: Position solution will be not change when moving.
Soft Event Detected: GPS speed > 8.0 m/s and no tacho pulses reported
(except heartbeats) for 15 GPS fixes.
Soft Event Cleared: Tacho pulse is reported, or unit is reset.
Action: Tacho labeled as “absent”. DR is suspended. Heading
measurement continues and gyro continues to be
calibrated.
Excessive tacho data is received for a long period of time
Condition cause: Wheels spinning, other tacho malfunction.
Effect before Action: Position fixes move at higher speed than actual position.
Soft Event Detected: Not implemented in ROM 15. Function partly done by
DPP recovery.
Reverse signal opposite to direction determined by GPS.
Condition cause: Disconnected reverse switch.
Effect before Action: Reverse driving is mistaken for forward driving, resulting
in incorrect position.
Soft Event Detected: Driving in reverse at raw GPS speed > 14 m/s.
Soft Event Cleared: Driving forward at raw GPS speed > 14 m/s.
Action: Direction Switch sense changed.
Large jump at power-up
Condition cause: Position in BBRAM incorrect (e.g., travel by ferry).
Effect before Action: Positions are offset by many kilometers after power-up.
Soft Event Detected: Offset between first three GPS points and DR position >
2000 m.
Action: Reset position to average GPS position.