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D Logs summary
156 MiLLennium Command Descriptions Manual
NAVA/B Waypoint Navigation Data
This log reports the status of your waypoint navigation progress. It is used in conjunction with the SETNAV
command.
REMEMBER: The SETNAV command must be enabled before valid data will be reported from this log.
NAVA
Structure:
Example:
$NAVA,640,333115.00,6399.6305,88.017,6396.9734,184.3929,657,51514.000,0,1
*11[CR][LF]
NOTE: All distances and angles are calculated using Vincenty's long line geodetic equations that operate on
the currently selected user datum.
See Figure D-1 for an illustration of navigation parameters.
$NAVA week seconds distance bearing along track
xtrack etaw
etas
nav status sol status
*xx
[CR][LF]
Field # Field type Data Description Example
1 $NAVA Log header $NAVA
2 week GPS week number 640
3 seconds GPS seconds into the week 333115.00
4 distance Straight line horizontal distance from current position to the destination waypoint, in metres
(see SETNAV command, Appendix C; Figure C-5). This value is positive when approaching
the waypoint and becomes negative on passing the waypoint.
6399.6305
5 bearing Direction from the current position to the destination waypoint in degrees with respect to True
North (or Magnetic if corrected for magnetic variation by MAGVAR command)
88.017
6 along track Horizontal track distance from the current position to the closest point on the waypoint arrival
perpendicular; expressed in metres. This value is positive when approaching the waypoint
and becomes negative on passing the waypoint.
6396.9734
7 xtrack The horizontal distance (perpendicular track-error) from the vessel's present position to the
closest point on the great circle line that joins the FROM and TO waypoints. If a "track offset"
has been entered in the SETNAV command, xtrack will be the perpendicular error from the
"offset track". Xtrack is expressed in metres. Positive values indicate the current position is
right of the Track, while negative offset values indicate left.
184.3929
8 etaw Estimated GPS week number at time of arrival at the "TO" waypoint along-track arrival
perpendicular based on current position and speed, in units of GPS weeks. If the receiving
antenna is moving at a speed of less than 0.1 m/sec in the direction of the destination, the
value in this field will be"9999".
657
9 etas Estimated GPS seconds into week at time of arrival at destination waypoint along-track arrival
perpendicular, based on current position and speed, in units of GPS seconds into the week.
If the receiving antenna is moving at a speed of less than 0.1 m/sec in the direction of the
destination, the value in this field will be"0.000".
51514.000
10 nav status Navigation data status, where 0 = good, 1 = no velocity, and 2 = bad navigation calculation 0
11 sol status Solution status as listed in Table D-1 1
12 *xx Checksum *11
13 [CR][LF] Sentence terminator [CR][LF]