Novatel OM-20000041 用户手册
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.
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:
two scenarios which affect how these logs are processed:
Case 1: ASCII messages (RTCMxA)
•
The NovAtel header ($RTCMx) and checksum terminator (*yz) must be stripped off at the
receiving end; then, the data will need to be converted from hexadecimal to binary before
the RTCM information can be retrieved.
receiving end; then, the data will need to be converted from hexadecimal to binary before
the RTCM information can be retrieved.
•
Provided that the GPSCard that is acting as a remote station has its ACCEPT command set
to “ACCEPT port COMMANDS” (which is the default setting), the receiving GPSCard will
recognize the NovAtel header ($RTCMxA) as a special data input command, and apply the
differential corrections data directly. No extra processing is required.
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.
retrieved.
•
These binary messages are not presently decoded directly by GPSCards, unlike the ASCII
messages.
messages.
ASCII
The format of the NovAtel ASCII version of an RTCM log is as follows:
Structure:
Example:
$RTCM3,597E7C7F7B76537A66406F49487F797B627A7A5978634E6E7C515544494
6*68[CR][LF]
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
format RTCM SC104 data
597E7C7F7B76537A66406F49487F79
7B627A7A5978634E6E7C5155444946
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