RTCM Message Map

TraceNav services deliver RTCM 3.x frames without modification. For the full specification, see the official RTCM 10403.3 document (available for purchase) at rtcm.org.

Frame layout

Field	Bytes	Description
`0xD3`	1	Frame sync marker
Length	2 (10-bit)	Payload length (excluding header + CRC)
Payload	n	Message type, data, parity bits packed MSB-first
CRC-24Q	3	Checksum over header + payload

Most RTCM parsers read payload bits into typed structures. For manual inspection, convert the payload to binary and consult the tables below.

Core reference messages

Msg ID	Name	Purpose	TraceNav usage
1005	Reference Station ARP	Absolute coordinates of the antenna reference point (ECEF)	Broadcast once per minute for VRS context
1033	Antenna Descriptor	Antenna type, serial number, and receiver ID	Sent hourly on managed bases
1230	GLONASS Code-Phase Bias	Aligns GLONASS FDMA frequencies	Included whenever GLONASS signals are enabled

Multi-Signal Messages (MSM)

TraceNav primarily streams MSM4 frames. They include pseudorange, carrier phase, Doppler, and C/N₀ for each satellite + signal.

Msg ID	Constellation	Content
1074	GPS MSM4	Observations for GPS L1/L2
1084	GLONASS MSM4	Observations for GLONASS G1/G2
1094	Galileo MSM4	Observations for E1/E5
1104	SBAS MSM4	WAAS/EGNOS/MSAS observations when enabled
1114	QZSS MSM4	QZSS L1/L2 observations when enabled
1124	BeiDou MSM4	Observations for B1/B2

Ephemeris messages

TraceAssist Ephemeris relies on dedicated message IDs that contain orbital parameters.

Msg ID	Constellation	Refresh rate
1019	GPS Broadcast Ephemeris	Every 5 seconds prior to GGA
1020	GLONASS Navigation Message	Every 5 seconds prior to GGA
1042	BeiDou Ephemeris	Every 5 seconds prior to GGA
1044	QZSS Ephemeris	Optional
1045	Galileo I/NAV Ephemeris	Optional
1046	Galileo F/NAV Ephemeris	Every 5 seconds prior to GGA

Once a rover sends its first valid GGA, the ephemeris repetition stops and only MSM + station messages remain. TraceAssist Ephemeris is enabled by default for all TraceNav sessions.

Example: Message 1005 decoding

A typical TraceNav log line looks like:

1005 0 25 d300133ed47e03fdf90ea0683475ad106d0918a798eedb1cb8

The final block (d300…) is the raw RTCM frame. Decoding the payload (after the 0xD3 header and 24-bit CRC) with the 10403.3 bit layout yields:

Field	Bits	Value	Notes
Message number	12	`1005`	Stationary Antenna Reference Point (no height)
Reference station ID	12	`1150`	Device identifier tied to TraceRouter credentials
ITRF realization year	6	`0`	`0` = frame unspecified (defaults to current TraceNav reference frame)
GPS / GLONASS / Galileo indicators	1 / 1 / 1	`1 / 1 / 1`	Station supports GPS, GLONASS, and Galileo signals
Reference-station flag	1	`1`	Confirms this is a reference (not transient) station
ARP ECEF-X	38	`-870641.6536 m`	Value is broadcast in 0.1 mm units (`-8 706 416 536`)
Single receiver oscillator	1	`0`	Separate oscillators per signal (common for network VRS)
Reserved	1	`0`	Always zero
ARP ECEF-Y	38	`-4956533.1347 m`	Signed two’s-complement value
Quarter-cycle indicator	2	`0`	Carrier-phase quarter-cycle offset not applied
ARP ECEF-Z	38	`3906834.2510 m`	Signed value in 0.1 mm units (TraceNav defaults to ITRF2020 @ current epoch)

Overview

Device setup

Manufacturer-specific setup

Products

Protocols & formats

Frame layout

Core reference messages

Multi-Signal Messages (MSM)

Ephemeris messages

Example: Message 1005 decoding

​Frame layout

​Core reference messages

​Multi-Signal Messages (MSM)

​Ephemeris messages

​Example: Message 1005 decoding

Frame layout

Core reference messages

Multi-Signal Messages (MSM)

Ephemeris messages

Example: Message 1005 decoding