What is NTRIP?

NTRIP (Networked Transport of RTCM via Internet Protocol) is a protocol for streaming GNSS correction data over the internet. It's built on HTTP/1.1 and designed specifically for delivering correction data to GNSS receivers in real time.

NTRIP is the delivery mechanism, but doesn't generate corrections itself or determine how they're calculated. Think of it as the "envelope" that carries correction data from a service provider to a receiver, regardless of which correction technique or data format is inside.

People in the GNSS industry sometimes use "NTRIP" loosely to refer to an entire correction service. In reality, NTRIP is just the messaging protocol or the packaging used to deliver the data, not the data or the technique that produced it.

What GNSS correction services use NTRIP?

A standard GNSS receiver can fix a location to meter-level accuracy. To reach centimeter-level accuracy, a high-precision receiver needs correction data, and NTRIP is one of the most common ways to deliver it. Several types of correction services rely on NTRIP, each with different tradeoffs:

RTK (Real Time Kinematic), including network RTK, uses corrections from a nearby base station or reference network. RTK-based solutions require two-way communication between the receiver and the correction service, which makes scaling to large numbers of users a challenge.

PPP-RTK combines the fast convergence of RTK with the broadcast scalability of PPP, using a sparser reference network than traditional network RTK.

PPP (Precise Point Positioning) uses global satellite orbit and clock corrections rather than a local reference station, trading some convergence speed for even broader, easier-to-scale coverage.

PPP-RTK and PPP typically only require one-way (unidirectional) communication, so they can be broadcast to large numbers of users over wide regions without the scaling constraints of a two-way RTK link.

As with the term NTRIP, GNSS industry insiders sometimes lump these services together and call the whole category "RTK" for short. In plain language, all of them serve the same goal: knowing your location with high accuracy, in real time, while in motion.

Diagram showing high-precision GNSS corrections for sub-meter and centimeter-level positioning

What data formats does NTRIP support?

NTRIP is format-agnostic — it can carry different types of correction data, as long as both ends of the stream agree on the format. Two of the most common are:

RTCM. Networked Transport of RTCM via Internet Protocol takes its name from RTCM, the data format most commonly used to structure GNSS correction messages. RTCM (Radio Technical Commission for Maritime Services) is a standards body that originally defined ways to communicate vessel positions; today, "RTCM" in the GNSS industry usually refers to its correction data format.

SPARTN. NTRIP can also stream corrections encoded in SPARTN, a more compact, purpose-built format commonly used with PPP-RTK services. SPARTN is designed to reduce bandwidth compared to RTCM, which matters for constrained links and budget-conscious applications.

Putting it all together

NTRIP is a messaging protocol based on HTTP and used for streaming GNSS corrections data over the internet for real time kinematic positioning, commonly referred to as RTK. NTRIP is the messaging format or the ‘packaging’ around the message being sent. RTCM is a standardized data format used to ‘structure’ the message itself. NTRIP protocol is typically used in combination with RTCM, but it can also be used in combination with other optimized data formats such as SPARTN.