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6 MiLLennium Command Descriptions Manual
• An RTCAOBS message contains reference station satellite observation information, and
should be sent once every 1 or 2 seconds.
• An RTCAREF message contains reference station position information, and should be
sent once every 10 seconds.
2. RT-20 requires that the reference station periodically transmit either the RTCA messages listed above (the
recommended option), or the RTCM SC-104 Type 3 & 59N messages:
• A Type 3 message contains reference station position information, and should be sent
once every 10 seconds (although it is possible to send it as infrequently as once every 30
seconds).
• A Type 59N message contains reference station satellite observation information, and
should be sent once every 2 seconds.
Further information on RTCA and RTCM message formats is contained in Chapter 6.
System Initialization
The RTK system is designed for ease of use: you set up the remote station, enter a command so that it accepts RT-
2 or RT-20 messages from the reference station, and are ready to go. There are options, however, which can be
used to adapt the system to a specific application. Some options apply only to the reference station, while others
apply only to the remote station. Detailed descriptions can be found in Appendix C, Commands Summary.
In the following sections, keep the following in mind:
• Dynamics modes. For reliable performance the antenna should not move more than 1-2
cm when in static mode. See the
RTKMODE commands in Chapter 2 and Appendix C for
more information.
• When using the
FIX POSITION command, the height entered must be in metres above mean
sea level; it will be converted to ellipsoidal height inside the receiver. You can enter an
undulation value, if desired, using the
UNDULATION command; if none is entered, the
receiver estimates an undulation with its internal table. The format of the optional station
ID field depends on whether RTCM or RTCA messages are being used: if RTCM, any
number from 0 - 1023 is valid, while if RTCA, any 4-character string of numbers and
upper-case letters, enclosed in quotation marks, is valid. See Appendix C for additional
information on the station id field.
• The COMn field refers to the serial port (either COM1 or COM2) to which data
communications equipment is connected. The serial port assignment at the reference and
remote stations need not be the same; e.g. a radio transmitter might be connected to
COM1 at the reference station, and a radio receiver to COM2 at the remote station.
INITIALIZATION FOR RTCA-FORMAT MESSAGING (RT-2 OR RT-20)
The following commands will enable RTCA-format messaging and allow RT-2 or RT-20 to operate with the
remote station either at rest or in motion. Note that the optional station health field in the existing FIX POSITION
command is not currently implemented in NovAtel’s RTCA messages, though it will be in the future.
1. At the reference station:
fix position lat,lon,height,
station id
log com
n
,rtcaref,ontime,interval
log com
n
,rtcaobs,ontime,interval
Example:
fix position 51.11358042,-114.04358013,1059.4105,”RW34”