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NTRIP (Networked Transport of RTCM via Internet Protocol) is the industry standard for streaming GNSS correction data. It wraps binary RTCM frames in a lightweight HTTP/1.0-style exchange so that rovers can connect through common firewalls and proxies without custom networking.

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End-to-end topology

Base station → NTRIP Server → TraceNav Caster → NTRIP Client (rover)
The caster behaves like a router: it accepts upstream uploads from bases or regional aggregators and forwards the selected stream to each connected rover.

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Client connection flow

1

(Optional) Fetch source table

GET / HTTP/1.0\r
User-Agent: NTRIP TraceClient/1.0\r
Authorization: Basic <base64(user:password)>\r
\r
TraceRouter replies with the standard NTRIP source table (STR;, CAS;, NET; entries). Many modern rovers skip this step and connect directly if the mountpoint is known.
2

Connect to /tracenav

GET /tracenav HTTP/1.0\r
User-Agent: NTRIP TraceClient/1.0\r
Authorization: Basic <base64(user:password)>\r
\r
3

Caster response

ICY 200 OK\r
<binary RTCM stream>
If a rover requests an invalid mountpoint, TraceRouter also returns the source table so the client can renegotiate.

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Base station uploads

TraceRouter exposes two mountpoints:
  • /tracenav — rover and client connections (HTTP GET)
  • /serve — base stations uploading correction data (HTTP SOURCE)
Reference stations authenticated to TraceNav push data with: 
SOURCE /serve HTTP/1.0\r
Source-Agent: NTRIP TraceServer/1.0\r
Authorization: Basic <base64(user:password)>\r
\r
<binary RTCM stream>
Credentials uniquely identify the base device. TraceRouter maps the upload to the correct project automatically—no manual mountpoint management is required.

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Authentication and security

  • Mechanism: HTTP Basic Auth (username:password Base64 encoded)
  • Transport: Plain TCP (no TLS in the NTRIP 1.0 spec)
  • TraceNav recommendation: Run clients inside a TLS tunnel, VPN, or cellular APN to secure credentials and data in transit.

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RTCM frame basics

Each RTCM 3.x packet contains:
  1. Sync header 0xD3
  2. 10-bit payload length
  3. Message payload (binary, message type + data)
  4. CRC-24Q checksum
TraceNav forwards frames byte-for-byte—no transcoding or re-encoding—so any NTRIP-compliant rover can ingest the data directly.
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