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C Commands Summary
MiLLennium Command Descriptions Manual 85
FIX POSITION
(RTK)
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, 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
WGS84 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
WGS84. Therefore, all differential corrections are based on WGS84, 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 metres
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
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