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1 Quick Start
18 MiLLennium GPSCard SW Version 4.503/4.52 Command Descriptions Manual Rev 2
NOTE 1: Entry of the station ID and health are optional. For a CMR correction type the station ID must be < 31.
NOTE 2: The accuracy of the reference station’s FIX POSITION setting will directly affect the accuracy of its
computed differential corrections. Good results at the rover station are dependent on the reference
station’s combined position errors being kept to a minimum (e.g., fix position error + multipath errors).
NOTE 3: The GPSCard performs all computations based on WGS84 and is defaulted as such, regardless of
DATUM command setting. The datum in which you choose to operate is converted from WGS84;
therefore, all differential corrections are based on WGS84. Ensure that any change in your operating
datum is set prior to FIX POSITION.
NOTE 4: When transmitting RTCM type data, the GPSCard has various options for assigning the number of data
bits per byte. Please see the GPSCard command RTCMRULE, Page 116 for further information
concerning RTCM data bit rule settings.
NOTE 5: The FIX POSITION “health” field entered will be reported in word 2 of the RTCM message frame
header.
Once the GPSCard has its position data fixed and is tracking three or more satellites, it is now ready to transmit
differential correction and observation data to the rover stations.
LOG BROADCAST DATA
Assuming that a data link has been established, use the GPSCard log command to send observation and differential
corrections data for broadcast to the rover stations.
Syntax:
Example:
log com1 rtcm ontime 5
NOTE: Ensure that the bit rate of the data link is suitable for the differential type, logging rate and maximum
message length of the data type being logged.
1.4 RTK MODE
NovAtel’s RTK system utilizes proprietary messaging as well as RTCM Types 18 and 19, and can also receive
CMR messages from a non-NovAtel base station. For more information on specific message formats please see
Chapter 4, Page 46.
NOTE: No guarantee is made that the MiLLennium will meet its performance specifications if non-NovAtel
accessories (e.g. antennas, RF cable) are used.
Data Communications Link
It is the user’s responsibility to provide a data communications link between the reference station and remote
station. The data transfer rate must be high enough to ensure that sufficient reference station messages reach the
remote station to keep extrapolation errors from growing too large; see Table 1-2.
Table 1-2 Latency-Induced Extrapolation Error
LOG port data ontime seconds
Time since last reference station observation Typical extrapolation error (CEP)
0-2 seconds 1 cm/sec
2-7 seconds 2 cm/sec
7-30 seconds 5 cm/sec