6 Message Formats

40 MiLLennium Command Descriptions Manual

ASCII
The format of the NovAtel ASCII version of an RTCM log is as follows:
Structure:
Example:
$RTCM3,597E7C7F7B76537A66406F49487F797B627A7A5978634E6E7C515544494
6*68[CR][LF]
BINARY
The format of the NovAtel binary version of an RTCM log is as follows:
RTCM OR RTCM1
This is the primary RTCM log used for pseudorange differential corrections. This log follows RTCM Standard
Format for Type 1 messages. It contains the pseudorange differential correction data computed by the reference
station generating this Type 1 log. The log is of variable length, depending on the number of satellites visible and
pseudoranges corrected by the reference station. Satellite specific data begins at word 3 of the message.
Structure:
(Follows RTCM Standard for Type 1 message)
Type 1 messages contain the following information for each satellite in view at the reference station:
Satellite ID
Pseudorange correction
Range-rate correction
Issue of Data (IOD)
When operating as a reference station, the GPSCard must be in FIX POSITION mode before the data can be correctly
logged.
When operating as a remote station, the GPSCard COM port receiving the RTCM data must have its ACCEPT
command set to "ACCEPT port RTCM".
REMEMBER: Upon a change in ephemeris, GPSCard reference stations will transmit Type 1 messages
based on the old ephemeris for a period of time defined by the DGPSTIMEOUT command. After the timeout, the
reference station will begin to transmit the Type 1 messages based on new ephemeris.
header rtcm data *xx [CR][LF]
Field # Field Type Data Description Example
1header NovAtel format ASCII header $RTCM3
2rtcm data hexadecimal representation of binary-
format RTCM SC104 data 597E7C7F7B76537A66406F49487F79
7B627A7A5978634E6E7C5155444946
3*xx Checksum *68
4[CR][LF] Sentence terminator [CR][LF]
Field # Data Bytes Format Offset
1 Sync 3 char 0
(header) Checksum 1 char 3
Message ID 4 integer 4
Message byte count 4 integer 8
2 RTCM SC104 data variable 12