DR + GPS
STARTER KIT REFERENCE MANUAL
Lassen DR + GPS Reference Manual 120
Invalid BBRAM detected on startup.
Condition cause: Hardware failure.
Effect before Action: If not cleared, very long time to first fix or worse.
Soft Event Detected: BBRAM checksum mismatch at power-up.
Action: Clear BBRAM.
Position recovery, solution snapped to GPS.
Condition cause: Incorrect position at start-up, or substantial drift of
DR+GPS position estimate.
Effect before Action: Large position offset between GPS and DR outputs for a
number of seconds.
Soft Event Detected: Compute average of “window” of recent unfiltered GPS
positions, propagated to current time using GPS
velocities. Soft event occurs if this window average
passes a series of criteria (see DR+GPS KF algorithm
document 45172-XX-SP) and the offset relative to the
DR position is large enough.
Action: The DR position is snapped to the window average.
Heading recovery, solution snapped to GPS.
Condition cause: Incorrect heading at start-up, or substantial drift of
DR+GPS heading estimate.
Effect before Action: Large heading offset between GPS and DR outputs for a
number of seconds.
Soft Event Detected: Compute average of “window” of recent raw GPS
headings, propagated to current time gyro
measurements. Soft event occurs if this window average
passes a series of criteria (see DR+GPS KF algorithm
document 45172-XX-SP) and the offset relative to the
DR heading is large enough.
Action: The DR heading is snapped to the window average.