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AgriBus-Caster Broadcast Messages and Mount Point Guide

This page summarizes the technical specifications (messages, satellite systems and intervals) of the correction data broadcast by AgriBus-Caster, the NTRIP casting service of Agri Info Design. Use it when connecting a third-party receiver, or when a receiver manufacturer asks which messages the base station broadcasts.

For an overview of the feature, see the news article “Receiver-compatible mount points and correction monitoring”.

The three mount points

AgriBus-Caster broadcasts the corrections of the same base station through three mount points. The host, port, user ID and password are shared; you only change the suffix of the mount point name.

Mount point Purpose
(base station ID) No conversion. Streams the base station output as-is. Use this normally
(base station ID)_MSM4 Compatibility mode. Normalized to standard MSM4 messages, for receivers unstable with the latest formats (e.g. MSM7)
(base station ID)_LEGACY For older receivers. Converted to legacy messages (1004/1012), for receivers without MSM support

You can find the mount point name of your base station on the Settings tab of the base station screen in AgriBus-Web.

Broadcast messages in detail

When a receiver manufacturer asks, give them the following list for the mount point you connect to.

1. No conversion (base station ID)

Streams the base station output as-is. For our AgriBus-GMiniR base stations:

  • Format: RTCM 3.3 (MSM)
  • Observations (every second): 1074/1077 (GPS), 1084/1087 (GLONASS), 1094/1097 (Galileo), 1124/1127 (BeiDou)
  • Auxiliary messages: 1005 (station position), 1008 (antenna info), 1230 (GLONASS code-phase biases)
  • Satellite systems: GPS / GLONASS / Galileo / BeiDou (all dual-frequency)

If you connect a third-party base station, the content follows that device’s own settings.

2. Compatibility mode (base station ID)_MSM4

Normalizes the base station output to standard MSM4 messages.

  • Format: RTCM 3.3 (MSM4 only)
  • Observations (every second): 1074 (GPS), 1084 (GLONASS), 1094 (Galileo), 1114 (QZSS), 1124 (BeiDou) — only the constellations the base station tracks
  • Auxiliary messages (every 5 seconds): 1006 (station position), 1033 (receiver and antenna info), 1230 (GLONASS code-phase biases)

3. For older receivers (base station ID)_LEGACY

Converts the corrections to legacy messages (RTCM 3.1 generation) for receivers without MSM support.

  • Format: RTCM 3.1 style
  • Observations (every second): 1004 (GPS L1/L2), 1012 (GLONASS L1/L2)
  • Auxiliary messages (every 5 seconds): 1006 (station position), 1008 (antenna info). 1033/1230 are not sent
  • Satellite systems: GPS / GLONASS only (the legacy format does not carry Galileo, QZSS, etc.)

Whole-second alignment of observation time tags

Some base stations (those built on u-blox receivers) broadcast RTCM observations with time tags slightly off the whole second (for example +1 millisecond every second). Most current receivers handle this without issues, but older receivers that expect whole-second time tags may struggle to reach an RTK fix.

_LEGACY also addresses this: the observation time is rounded to the nearest whole second, and the observations (pseudorange and carrier phase) are projected to that time using the per-satellite range rate before broadcasting (available since November 5, 2026). The effect on accuracy is below a millimeter, so receivers that expect whole-second time tags can be used as-is.

How to check what is actually broadcast

  • AgriBus-Web: the Quality tab of the base station screen lists the message types actually received, their rate and the last-received time. This is the most reliable way to cross-check against the specifications above
  • NTRIP source table: when you request the source table from an NTRIP client, the STR row of each mount point lists the broadcast format and messages (format-details)

Notes

  • _MSM4 / _LEGACY are additional outputs of the same base station. There is no extra charge, and the usage conditions (plan, concurrent connections) are shared with the regular mount point
  • If you connect a third-party base station, some outputs may not be available depending on the input format (if the base station broadcasts only MSM4-level messages, _LEGACY carries GPS only; if it broadcasts only legacy messages, _MSM4 / _LEGACY are not available)
  • Some receivers may not improve. If in doubt, contact us with your receiver model