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4 Operation
4.7.1 PSEUDORANGE (PSR) DIFFERENTIAL POSITIONING
PSR positioning utilizes the satellite pseudorange information from the reference and remote receiver. The
reference receiver at a known location broadcasts the difference between the measured range to a satellite and the
true range. Currently, the MiLLennium-GLONASS GPSCard supports RTCM standard types 31 and 34 for
GLONASS operation. Type 31 messages are the equivalent of Type 1 for GPS while Type 34 are equivalent to
Type 9 for GPS. Descriptions of the RTCM message types can be found in RTCM SC-104 version 2.2 available
from the Radio Technical Commission for Maritime services. The contact information for this organization is
given in Appendix F of the MiLLennium Commands Description Manual.
Type 9 and Type 34 message types contain only a subset of the full correction set and are intended for use with
stable external oscillators at the reference station. Generally, the update rate of the corrections should be at least
once every five seconds. The default time-out values for GPS and GLONASS corrections is 60 seconds but are
user-configurable using the DGLOTIMEOUT (see Page 82)and DGPSTIMEOUT (refer to the MiLLennium
Command Descriptions Manual) commands. GLONASS measurements, which do not suffer from Selective
Availability (SA), will degrade at a slower rate than GPS after about 30 seconds. The following sets of commands
will enable PSR differential positioning for two MiLLennium-GLONASS GPSCard receivers assuming a radio
link has been provided. Two examples have been shown for the reference station representing the full correction
set (RTCM Type 1,31) and partial correction set (RTCM Type 9,34) configurations.
1A
Reference Station Initialization (full correction message)
fix position lat, lon, height, station ID
log comn,rtcm1,ontime,interval
log comn,rtcm31,ontime,interval
example:
fix position 51.11358042,-114.04358013,1059.4105,1024
log com1, rtcm1, ontime, 2
log com1, rtcm31, ontime, 2
1B
Reference Station Initialization (partial correction message)
fix position lat, lon, height, station ID
log comn,rtcm9,ontime,interval
log comn,rtcm34,ontime,interval
example:
fix position 51.11358042,-114.04358013,1059.4105,1024
log com1, rtcm9, ontime, 2
log com1, rtcm34, ontime, 2
2
Remote Station Initialization
accept comn, rtcm
example:
accept com2, rtcm
NOTE:
The MiLLennium-GLONASS GPSCard also supports the NovAtel ASCII and Binary versions of the
new RTCM Type 31 and 34 messages. These are of the same form but are wrapped in a NovAtel header
and checksum. The ASCII version has the RTCM data portion converted to hexadecimal before
transmission. If the COM port on the remote receiver is set to accept COMn commands, the receiver will
be able to decode and use the $RTCMA, $RTCM9A, $RTCM31A and $RTCM34A message types. See
the Message Formats section of the MiLLennium Commands Description Manual for more details.
40
GPS/GLONASS Receiver User Manual Rev 1
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