RTCMV3 Standard Logs
Platform: |
OEM719, OEM729, OEM7500, OEM7600, OEM7700, OEM7720, PwrPak7, CPT7, CPT7700, SMART7 |
NovAtel’s RTCMv3 logs are implementations of the messages described by the RTCM SC-104 committee’s “Differential GNSS (Global Navigation Satellite Systems) Services – Version 3” standard. These messages are primarily intended to support RTK operations. They are also an alternative raw data format to NovAtel’s proprietary messages.
The RTCMv3 logs can be divided into several categories that are described below. An RTK base station must minimally transmit one or more observable message, together with one or more station and antenna message. The GENERATERTKCORRECTIONS command illustrates an appropriate set of messages and is an easy way to configure logging.
Example Input:
interfacemode com2 none RTCMV3
fix position 51.1136 -114.0435 1059.4
thisantennatype NOV702
log com2 rtcm1006 ontime 10
log com2 rtcm1230 ontime 10
log com2 rtcm1033 ontime 10 2
log com2 rtcm1004 ontime 1
log com2 rtcm1012 ontime 1
Example Input using MSM4 messages:
interfacemode com1 none rtcmv3 off
thisantennatype nov850
fix position 51.1136 -114.0435 1059.4
log com1 rtcm1006 ontime 10
log com1 rtcm1230 ontime 10
log com1 rtcm1033 ontime 10 2
log com1 rtcm1074 ontime 1
log com1 rtcm1084 ontime 1
log com1 rtcm1094 ontime 1
log com1 rtcm1124 ontime 1
Legacy Observable Messages
The legacy observable messages contain GPS and GLONASS code and phase observables. The extended messages additionally contain the C/N0.
Log Name |
Message ID |
Description |
---|---|---|
RTCM1001 |
772 |
GPS L1-only observables, basic |
RTCM1002 |
774 |
GPS L1-only observables, extended |
RTCM1003 |
776 |
GPS L1/L2 basic observables, basic |
RTCM1004 |
770 |
GPS L1/L2 basic observables, extended |
RTCM1009 |
885 |
GLONASS L1-only observables, basic |
RTCM1010 |
887 |
GLONASS L1-only observables, extended |
RTCM1011 |
889 |
GLONASS L1/L2 basic observables, basic |
RTCM1012 |
891 |
GLONASS L1/L2 basic observables, extended |
MSM Observable Messages
The Multiple Signal Messages (MSM) are observable messages for all current GNSS systems. They provide a standardized framework for message content and are designed to support future systems and signals.
Sending legacy (1001-1004 and 1009-1012) and MSM messages in the same stream can cause problems for remote RTK users and is not recommended.
Each GNSS system has a set of seven MSM types numbered from 1 to 7. The MSM type for each GNSS system provides the same generic information. Generally, as the MSM number increases, more information is available in the messages. For example, MSM1 for each GNSS system provides the code measurements for the system, while MSM3 provides both the code and phase.
The information encoded in each MSM variant is described in Table: MSM Type Descriptions for the descriptions of each of the seven MSM types. For RTK operations, MSM3 is minimally recommended.
Table: MSM Log Names lists the MSM message name and Table: MSM Message IDs lists the message IDs.
Station and Antenna Messages
The station and antenna messages listed in Table: Station and Antenna Messages provide the base station’s coordinates and hardware. Remote RTK users require this information so that they can position themselves relative to a base station.
-
Message Type 1005 provides the Earth-Centered, Earth-Fixed (ECEF) coordinates of the Antenna Reference Point (ARP). The ARP is an explicit physical point on the antenna, typically the center of its base. It is related to the antenna phase center from where the measurements are emitted via the Phase Center Offsets (PCOs). The PCOs can be set using the THISANTENNAPCO command or THISANTENNATYPE command. If the PCOs are not set, then the coordinates transmitted by Message types 1005 and 1006 will be those that the receiver is fixed to by the FIX command.
-
Message Type 1006 is the same as 1005 but additionally provides the antenna height. This value is always set to zero by the receiver firmware.
-
Message Type 1007 provides the base station antenna type. Conventionally, the antenna name from the International GNSS Service (IGS) is used. The antenna name can be set using the THISANTENNATYPE command.
-
Message Type 1008 is the same as 1007 but additionally provides the antenna serial number. The serial number is always set to null by the receiver firmware.
-
Message Type 1033, like message types 1007 and 1008, also provides the antenna information. Message type 1033 additionally provides the receiver type and firmware version. The primary use of this information is to more-easily enable RTK rovers to fix their GLONASS ambiguities. This information is filled automatically and appropriately by the receiver firmware.
For a receiver operating as an RTK base station, the recommended messages to transmit are 1006 and 1033. With these messages remote RTK users have all the information describing the base station.
Ephemeris Messages
The ephemeris messages listed in Table: Ephemeris Messages provide the satellite ephemerides. For RTK operations this information is optional, as RTK rovers will be downloading their own ephemerides directly from the satellites.
There are two messages for each ephemeris type. For the messages logged ONTIME (e.g. LOG RTCM1019 ONTIME 10) a single satellite’s ephemeris is output at each ONTIME interval. The ephemerides will be cycled through in numerical order. For the messages logged ONCHANGED (e.g., LOG RTCM1019ASYNC ONCHANGED), new or changed ephemerides will be output as soon as they are available.
GLONASS Bias Information Message
Message 1230 communicates the GLONASS Code-Phase Bias (CPB) information. This information allows RTK rovers to compensate for differences in biases between themselves and the base station, enabling or improving the resolution of GLONASS ambiguities.
CPB values for all GLONASS FDMA signals available in the data stream of both MSM and Legacy (1081-1088 and 1009-1012) are mandatory for full GLONASS interoperability.
With some base stations, message 1033 is not sufficient for full GLONASS interoperability. The message 1033 was not originally designed to compensate for CPB and therefore message 1230 has been developed to improve GLONASS interoperability and should be used to assure full interoperability.
Log Name |
Message ID |
RTCM Message Type |
Description |
---|---|---|---|
RTCM1230 |
1655 |
1230 |
GLONASS L1 and L2 Code-Phase Biases |