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 |
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 |
Example: Message 1005 decoding
A typical TraceNav log line looks like: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) |