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H.2.13 VLHA/BVELOCITY, LATENCY, & DIRECTION OVER GROUND
The actual speed and direction of the antenna over ground is provided. The VLHA/B log provides a measure of the
latency in the velocity time tag and a new velocity status word which gives you quality velocity information. The
velocity status indicates varying degrees of velocity quality. To ensure healthy velocity, the position solution status
must also be checked. If the solution status is non-zero, the velocity will likely be invalid. Also, it includes the age
of the differential corrections used in the velocity computation. It should be noted that the MiLLennium-
GLONASS GPSCard does not determine the direction a vessel, craft, or vehicle is pointed (heading), but rather the
direction of motion of the antenna relative to ground.
VLHA
Structure:
$VLHA
week
seconds
hor speed
direction wrt True North
1
solution status
velocity status
1
NOTES:
See Table H.8 (Page 111)
Example:
$VLHA,991,489504.00,0.500,0.000,0.099,56.492,0.139,0,3*3B[CR][LF]
Value
0
1
2
3
4
5
State
0
Solution computed
1
Insufficient observations
2
No convergence
3
Singular A
4
Covariance trace exceeds maximum (trace > 1000 m)
5
Test distance exceeded (maximum of 3 rejections if distance > 10km)
6
Not yet converged from cold start
7
Height or velocity limit exceeded. (In accordance with COCOM export licensing restrictions)
8
Bad integrity
Higher numbers are reserved for future use
GPS/GLONASS Receiver User Manual Rev 1
velocity time tag latency
2
*xx
2
See Table H.7 below
Table H.7 Velocity Status
Velocity computed from differentially corrected carrier phase data
Velocity computed from differentially corrected Doppler data
Old velocity from differentially corrected phase or Doppler (higher
latency)
Velocity from single point computations
Old velocity from single point computations (higher latency)
Invalid velocity
Higher values reserved for future use
Table H.8 GPSCard Solution Status
T
PA Matrix
age of GPS data
vert speed
[CR][LF]
Description
Description
H NovAtel Format Logs
111
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