ntrip-rtcm3-to-rtcm2p3

An NTRIP receiver + LAN rebroadcaster that also converts an RTCM 3.x reference stream into RTCM 2.3 DGPS corrections, so that legacy single-band receivers that only understand RTCM 2.3 (e.g. the u-blox 7) can benefit from a modern RTCM3-only correction network.

Built incrementally with a full test suite; every conversion stage is cross-checked against independent implementations (see the Validation docs).

📖 Documentation (Read the Docs)

Why

Modern correction networks (e.g. Geoscience Australia's AUSCORS) broadcast RTCM 3.x only. A u-blox 7 / NEO-7 accepts RTCM 2.3 DGPS corrections but has no RTCM3 decoder. No off-the-shelf tool converts RTCM3 → RTCM 2.3 (RTKLIB's str2str can only emit RTCM3; the BKG NTRIP Client (BNC) only decodes RTCM2). RTCM 2.3 Type 1 messages are derived pseudorange corrections, not a reformat — they must be computed from the base station's observations, its known position, and satellite positions from broadcast ephemeris.

Pipeline

        obs + base position                 broadcast ephemeris
   (RTCM3 MSM7 1077, 1006)                 (RTCM3 1019, separate mount)
             │                                       │
             ▼                                       ▼
      decode pseudoranges  ───────────────►  satellite position + clock
             │                                       │
             └───────────────┬───────────────────────┘
                             ▼
                   per-SV PRC / RRC  (DGPS reference-station math)
                             ▼
                   encode RTCM 2.3 Type 1 / 3 (parity, IOD, scaling)
                             ▼
              serve as a local NTRIP mount alongside the raw RTCM3

Development

uv run --extra dev pytest        # test suite
uv run --extra dev ruff check .  # lint

License

Apache-2.0. See LICENSE.