Novatel OM-20000053 Rev 2 ASCII, BINARY, RTCM OR RTCM1

4 Message Formats
MiLLennium GPSCard SW Version 4.503/4.52 Command Descriptions Manual Rev 2 51
along with other NovAtel ASCII and binary data over a common communications port. As per the usual
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
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