Leica GR10, Operational Manual

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Appendix C: RTCM Messages
RTCM Message Types
Background information
Radio Technical Commission for Maritime services. Commission set up to define a differential data link to relay GPS
correction messages from a monitor station to a field user.
RTCM v.2.x
Type Description
1 Differential GPS Corrections. Message Type 1 provides the pseudorange correction (PRC(t))
for any user receiver GPS measurement time "t". The Type 1 Message contains data for all
satellites in view of the reference station.
2 Delta Differential GPS Corrections. Upon a change in ephemeris, the reference station
broadcasts a Type 2 message paired with a Type 1 message, and continues to broadcast
Type 2 messages over a period of several minutes following a change in satellite navigation
data in order to accommodate users coming on line. The message contains the difference in
the pseudorange and range rate corrections caused by the change in satellite navigation data.
The general format is the same as that of a Type 1 Message.
3 GPS Reference Station Parameters. Message Type 3 contains reference station information. It
includes the GPS coordinates (Earth-Centered-Earth-Fixed (ECEF)) of the reference station
antenna to the nearest centimeter. WGS-84 is the recommended reference datum. If a datum
other than WGS-84 is used, Message Type 4 will be broadcast frequently to inform the users
of the datum being used for the reference station coordinates.
9 GPS Partial Correction Set. The Type 9 Message serves the same purpose as the Type 1
Message, in that it contains the primary differential GPS corrections. However, unlike Type
1's, Type 9 Messages do not require a complete satellite set.
18 RTK Uncorrected Carrier Phases. GPS/GLONASS Satellite constellation indicator are used to
differentiate between the satellite systems. Hence, there are individual messages for GPS and
GLONASS satellites and for each frequency. The GNSS time of measurement is referenced to
GPS time for GPS satellites and to GLONASS time for GLONASS satellites. Note that
GLONASS satellites are supported in v2.3 only.
19 RTK Uncorrected Pseudoranges. GPS/GLONASS Satellite constellation indicator are used to
differentiate between the satellite systems. Hence, there are individual messages for GPS and
GLONASS satellites and for each frequency. The time of measurement is referenced to GPS
time for GPS satellites and to GLONASS time for GLONASS satellites. Note that GLONASS
satellites are supported in v2.3 only.
20 RTK Carrier Phase Corrections. Same handling as for Type 18. Note that GLONASS satellites
are currently not supported.
21 RTK/High Accuracy Pseudorange Corrections. Same handling as for Type 19. Note that
GLONASS satellites are currently not supported.
23 (v2.3
only)
Antenna Type Definition Record. Message Type 23 provides the information on the antenna
type used on the reference station. The RTCM commission adopted the naming convention
from the IGS equipment-naming table as supplied by the International GNSS Service Central
Bureau (IGS CB).This table provides a unique antenna descriptor for antennas used for high-
precision surveying type applications.
24 (v2.3
only)
Antenna Reference Point (ARP). Message Type 24 solves the problem of referencing the L1
phase center by utilizing the Antenna Reference Point (ARP), which is used throughout the
International GNSS Service (IGS).
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