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.

Legacy Observable Messages

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.

MSM Type Descriptions

Message

Description

MSM1

Provides the code measurements.

MSM2

Provides the phase measurements.

MSM3

Provides the data from MSM1 (code) and MSM2 (phase) in a single message.

MSM4

Provides all the data from MSM3 (code and phase) and adds the CNR measurements.

MSM5

Provides all the data from MSM4 (code, phase and CNR) and adds the doppler measurements.

MSM6

Provides the same information as MSM4, but has extended resolution on the measurements.

MSM7

Provides the same information as MSM5, but has extended resolution on the measurements.

Table: MSM Log Names lists the MSM message name and Table: MSM Message IDs lists the message IDs.

MSM Log Names

Message

GPS

GLONASS

Galileo

QZSS

BeiDou

MSM1

RTCM1071

RTCM1081

RTCM1091

RTCM1111

RTCM1121

MSM2

RTCM1072

RTCM1082

RTCM1092

RTCM1112

RTCM1122

MSM3

RTCM1073

RTCM1083

RTCM1093

RTCM1113

RTCM1123

MSM4

RTCM1074

RTCM1084

RTCM1094

RTCM1114

RTCM1124

MSM5

RTCM1075

RTCM1085

RTCM1095

RTCM1115

RTCM1125

MSM6

RTCM1076

RTCM1086

RTCM1096

RTCM1116

RTCM1126

MSM7

RTCM1077

RTCM1087

RTCM1097

RTCM1117

RTCM1127

MSM Message IDs

Message

GPS

GLONASS

Galileo

QZSS

BeiDou

MSM1

1472

1479

1486

1648

1592

MSM2

1473

1480

1487

1649

1593

MSM3

1474

1481

1488

1650

1594

MSM4

1475

1482

1489

1651

1595

MSM5

1476

1483

1490

1652

1596

MSM6

1477

1484

1491

1653

1597

MSM7

1478

1485

1492

1654

1598

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.

Station and Antenna Messages

Log Name

Message ID

RTCM Message Type

Description

RTCM1005

765

1005

Stationary RTK Base Station Antenna Reference Point (ARP)

RTCM1006

768

1006

Stationary RTK Base Station ARP with Antenna Height

RTCM1007

852

1007

Extended Antenna Descriptor and Setup Information

RTCM1008

854

1008

Extended Antenna Reference Station Description and Serial Number

RTCM1033

1097

1033

Receiver and antenna descriptors

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.

Ephemeris Messages

Log Name

Message ID

RTCM Message Type

Description

RTCM1019

893

1019

GPS Ephemerides, logged ONTIME

RTCM1019ASYNC

2088

1019

GPS Ephemerides, logged ONCHANGED

RTCM1020

895

1020

GLONASS Ephemerides, logged ONTIME

RTCM1020ASYNC

2089

1020

GLONASS Ephemerides, logged ONCHANGED

RTCM1042

2171

1042

BeiDou Ephemerides, logged ONTIME

RTCM1042ASYNC

2170

1042

BeiDou Ephemerides, logged ONCHANGED

RTCM1044

2177

1044

QZSS Ephemerides, logged ONTIME

RTCM1044ASYNC

2176

1044

QZSS Ephemerides, logged ONCHANGED

RTCM1045

2173

1045

Galileo F/NAV Ephemerides, logged ONTIME

RTCM1045ASYNC

2172

1045

Galileo F/NAV Ephemerides, logged ONCHANGED

RTCM1046

2175

1046

Galileo I/NAV Ephemerides, logged ONTIME

RTCM1046ASYNC

2174

1046

Galileo I/NAV Ephemerides, logged ONCHANGED

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.

GLONASS Bias Information Message

Log Name

Message ID

RTCM Message Type

Description

RTCM1230

1655

1230

GLONASS L1 and L2 Code-Phase Biases