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4 Message Formats
50 MiLLennium GPSCard Software Version 4.50 Command Descriptions Manual Rev 1
convention, an “A” at the end of the log name denotes the NovAtel ASCII version (e.g. RTCM1A), and a “B”
denotes the NovAtel binary version (e.g. RTCM1B). These logs contain the same data that is available in the
corresponding RTCM Standard Format messages; however, the data has been “packaged” into NovAtel-format
messages.
These NovAtel-format logs are not in pure RTCM SC-104 format and are not directly usable as such. There are
two scenarios which affect how these logs are processed:
Case 1: ASCII messages (RTCMxA)
• The NovAtel header ($RTCMx) and checksum terminator (*yz) must be stripped off at the
receiving end; then, the data will need to be converted from hexadecimal to binary before
the RTCM information can be retrieved.
• Provided that the GPSCard that is acting as a remote station has its ACCEPT command set
to “ACCEPT port COMMANDS” (which is the default setting), the receiving GPSCard will
recognize the NovAtel header ($RTCMxA) as a special data input command, and apply the
differential corrections data directly. No extra processing is required.
Case 2: Binary messages (RTCMxB)
• The 12-byte NovAtel header must be stripped off before the RTCM information can be
retrieved.
• These binary messages are not presently decoded directly by GPSCards, unlike the ASCII
messages.
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
header rtcm data *xx [CR][LF]
Field # Field Type Data Description Example
1 header NovAtel format ASCII header $RTCM3
2 rtcm 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