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C Commands Summary
100 MiLLennium GPSCard SW Version 4.503/4.52 Command Descriptions Manual Rev 2
FIX POSITION
Invoking this command will result in the GPSCard position being held fixed. A computation will be done to solve
local clock offset, pseudorange, and pseudorange differential corrections. This mode of operation can be used for
time transfer applications where the position is fixed and accurate GPS time output is required (see the CLKA/B
and TM1A/B logs, Appendix D for time data).
As well, this command must be properly initialized before the GPSCard can operate as a GPS pseudorange
reference station. Once initialized, the receiver will compute pseudorange differential corrections for each satellite
being tracked. The computed differential corrections can then be output to remote stations by utilizing any of the
following GPSCard differential corrections data log formats: RTCM, RTCMA, RTCMB, CMR, RTCA, RTCAA
or RTCAB. The reference station servicing RT-
20 remote receivers must log RTCM3 and RTCM59(N)
pseudorange and carrier- phase observation data in order for the RT-
20 remote receiver to compute double
difference carrier phase solutions.
The values entered into the FIX POSITION command should reflect the precise position of the reference station
antenna phase centre. Any errors in the FIX POSITION coordinates will directly bias the pseudorange corrections
calculated by the reference receiver.
The GPSCard performs all internal computations based on WGS
84 and the datum command is defaulted as such.
The datum in which you choose to operate (by changing the DATUM command) will internally be converted to
and from WGS
84. Therefore, all differential corrections are based on WGS-84, regardless of your operating datum.
The GPSCard will begin logging differential data while tracking as few as three healthy satellites. See Appendix A
for further discussions on differential positioning.
The FIX POSITION command will override any previous FIX HEIGHT or FIX POSITION command settings.
Use the UNFIX command to disable the FIX POSITION setting.
Syntax:
Example:
fix position 51.3455323,-114.289534,1201.123,1002,0
The above example configures the receiver as a reference station with fixed coordinates of:
Latitude N 51º 20' 43.9163" (WGS84 or local datum)
Longitude W 114º 17' 22.3224"
Height above sea level 1201.123 meters
Station ID 1002
RTCM health 0
FIX POSITION lat lon height station id [RTCM stn health]
Syntax Range Value Description Default Example
FIX POSITION - Command unfix fix position
lat 0 to ± 90.0
(Up to 8 decimal places are shown in the RCCA
log but more precision is determined internally)
Latitude (in degrees/decimal degrees)
of fixed reference station antenna in
current datum. A negative sign implies
South latitude.
51.3455323
lon 0 to ± 360.0
(Up to 8 decimal places are shown in the RCCA
log but more precision is determined internally)
Longitude (in degrees) of fixed
reference station antenna in current
datum. A negative sign implies West
longitude.
-114.289534
height -1,000 to 20,000,000 Height (in metres) above the geoid of
reference station in current datum.
1201.123
station id 0 to 1023 (10 bits) for RTCM output
“xxxx” for RTCA output
where ”xxxx” are four alphanumeric characters,
entered between double quotes. For CMR, the
station ID should be <
31.
Specify a reference Station
identification number (optional entry)
(see SETDGPSID)
1002
RTCM
reference
station health
0-7
where 0-5 Specified by user
6 Reference station
transmission not monitored
7 Reference station not working
Specify RTCM reference station health
(optional)
(This field will only be reported in
RTCM message header - word 2.)
6 0