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Table 6.67: $GPMSG Response, RTCM Message Type 16 (continued)
RTCM type 18 is the uncorrected carrier phase message used to transmit data to the
rover for RTK processing. The format for RTCM type 18 is:
Table 6.68 outlines the $GPMSG response message structure for RTK Uncorrected
Carrier Phases (Type 18)
Command/Response Formats
Item
232008.00
Current time in hours, minutes and seconds
THIS IS A....
Message content
5C
Message checksum in hexadecimal
$GPMSG,d1,d2,f1,d3,d4,d5,m1,s1,d6,d7,n(d8,d9,d10,d11,f2)*cc
Table 6.68: $GPMSG Structure for RTCM Message Type 18
Field
d1
RTCM type, 18
d2
Station identifier, 0000 to 1023
f1
Z count in seconds and tenths, 0000.0 to 3600.0
d3
Sequence number, 0 to 7
d4
Station health, 0 to 7
d5
Total number of characters after the time item, 000 to 999
m1
Current UTC time of position computation in hours, minutes,
and seconds
s1
GPS / GLONASS Constellation Indicator
d6
Frequency Indicator: "00": L1 message, "01": L2 message,
"10","11" :Reserved
d7
GNSS Time of measurement (GPS or GLONASS time) (added
to Z-Count)
The following data is displayed for each Satellite in the message:
d8
Multiple message indicator (1 = more messages will follow with
same time tag, 0 = last message)
d9
GPS (PRN Range 0-31) or GLONASS (Slot number 1-24)
Satellite ID
d10
Data Quality Indicator (See RTCM Paper 88-97/SC104-156
Version 2.2)
Description
Description
155
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