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Longitude
E/W Indicator
Speed Over Ground
Course Over Ground
Date
Magnetic Variation(1)
Checksum
<CR> <LF>
1. SiRF Technology Inc. does not support magnetic declination. All "course over ground" data are geodetic
WGS84 directions.
5.1.6 Course Over Ground and Ground Speed (VTG)
Table 5-10 contains the values for the following example:
$GPVTG,309.62,T, ,M,0.13,N,0.2,K*6E
Table 5-10 VTG Data Format
Name
Message ID
Course
Reference
Course
Reference
Speed
Units
Speed
Units
Checksum
<CR> <LF>
1. SiRF Technology Inc. does not support magnetic declination. All "course over ground" data are geodetic
WGS84 directions.
5.2 RTCM Received Data
The default communication parameters for DGPS Input are 9600 baud, 8 data bits, stop bit, and no parity.
Position accuracy of less than 5 meters can be achieved with the GR-212 by using Differential GPS (DGPS)
real-time pseudo-range correction data in RTCM SC-104 format, with message types 1,2, or 9. As using
DGPS receiver with different communication parameters, GR-212 may decode the data correctly to generate
accurate messages and save them in battery-back SRAM for later computing.
6. Earth Datums
6.1 Earth Datums
The following is a list of the GR-212 earth datum index and the corresponding earth datum name:
Item
1
Adindan - Ethiopia
2
Afgooye – Somalia
3
Alaska, Conus – North American 1983
4
Albania – S-42 (Pulkovo 1942)
5
Argentina
6
Australia
12158.3416
W
0.13
knots
309.62
degrees
120598
degrees
*10
Example
Units
$GPVTG
309.62
degrees
T
degrees
M
0.13
knots
N
0.2
km/hr
K
*6E
Datum
dddmm.mmmm
E=east or W=west
True
ddmmyy
E=east or W=west
End of message termination
Description
VTG protocol header
Measured heading
True
Measured heading
Magnetic(1)
Measured horizontal speed
Knots
Measured horizontal speed
Kilometers per hour
End of message termination
Reference Ellipsoid
Clarke 1880
Krassovsky
GRS 1980
Krassovsky 1940
South American 1969
Australian – National
HOLUX
Data name
Data1.dat
Data2.dat
Data3.dat
Data63.dat
Data4.dat
Data70.dat
11
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