ComNav Commander P2 & P2VS Installation & Operation Appendices
Document PN 29010074 V4.1 - 186 -
Sentence & Data Priority
A number of the various data values used by the autopilot can be received in one or more
different sentences. For example, Boat Speed can be received in VTG, VHW, VBW, RMA or
RMC.
If a particular data value is received in more than one sentence, then the value in the
highest-priority sentence will be the one used by the autopilot.
•
An item of data will be taken from the sentence without a checksum only if the data is
not found in any sentences with a valid checksum – even if the no-checksum
sentence is of higher priority, per the table below – than the with-checksum
sentence(s).
•
In some cases, if the invalid-checksum condition persists long enough, an INVALID
CRS DATA, SPEED DATA, &/or HEADING error will occur (see page 196).
It is also worth noting that the names of some sentences reflect the data (or else just the
“main data”) in that sentence. For example, the BOD sentence contains “Bearing Origin to
Destination” data.
But that does not always mean that those “named” sentences are the only source for that
data – for example, BOD data could also come from the APB sentence.
Sentence
Priority
(higher to lower)
Sentence Data Used
1 *MWV True or Apparent Wind Angle & Speed
2 *VWR Apparent Wind Angle & Speed
3 *VWT True Wind Angle & Speed
4 *GLL Latitude & Longitude
5 *RMC Latitude & Longitude,
Boat Speed,
Magnetic Variation
6 *RMA Latitude & Longitude,
Boat Speed
7 *APB Cross-Track Error,
Arrival Circle Entered,
Bearing Origin to Destination Magnetic or True,
Waypoint ID,
Bearing Present to Destination Magnetic or True,
Heading to Steer Magnetic or True
8 *RMB Cross-Track Error,
Waypoint ID,
Range ,
Bearing Present to Destination True,
Arrival Circle Entered or Perpendicular Passed at Waypoint
9 *HSC
Heading to Steer Magnetic and True
10 *APA Cross-Track Error,
Arrival Circle Entered,
Perpendicular Passed at Waypoint,
Bearing Origin to Destination Magnetic,
Waypoint ID
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