DR + GPS
STARTER KIT REFERENCE MANUAL
Lassen DR + GPS Reference Manual 99
This message provides the first 20 seconds (or more) of buffered DR information.
If the host takes significant time to boot up, this provides the recent path for map-
matching purposes. The host should also request start-up information (0x16-02)
and health information (0x16-01) on late boot-up. Once the message is queried,
the data is frozen, and subsequent queries return the same data.
Validity Bits:
The “all data” flag bit is set if the data buffer
contains all data since power-up.
The “rolling start” bit will be set if a tacho pulse
(other than a heartbeat) is detected in the first 200
ms.
Delta-distance is “valid” if the tacho was calibrated
at start-up.
Delta-heading is “valid” if the gyro was calibrated
before vehicle started moving.
Time source and position, and heading validity bits
are taken from the most recent 0x30-02 message.
These can be used with the current timetag,
position, and heading to formulate a HIPPO map-
match message.
An array of up to 20 delta-distances and delta-headings are in the message.
These values will have been corrected with the estimate of ZRO and DPP current
at the time. Each will be over an interval lasting about one second, except for the
first and last intervals. The intervals are reported in reverse order, from newest
(most-recent) first, to oldest (first recorded). If the module has collected less than
twenty intervals of data, the unrecorded array elements will be set to zero. These
zero-distance elements will have no effect on map-matching algorithms.
The oldest (first-recorded) interval lasts from power-up until the first integer
second at which motion is detected.
The most recent interval for delta-distance and delta-heading gives the data
between the most recent integer second and the request, so it may not be a
complete second. If no motion has been recorded since power-up, this is the only
interval reported and it may be much longer than one second.
Distance accuracy is relative to the total distance traveled (the sum of all the
intervals). The accuracy of each one-second segment should be scaled
proportionately.
Delta Heading accuracy is over each one-second interval, and is roughly the
same for each of the intervals except the most recent, which may be more
accurate.