Ntrip stands for an application-level protocol for streaming Global Navigation Satellite System (GNSS) data over the Internet.

It is a generic, stateless protocol based on the Hypertext Transfer Protocol HTTP/1.1. The HTTP objects are enhanced to GNSS data streams. Ntrip is an RTCM standard designed for disseminating differential correction data (e.g in the RTCM-104 format) or other kinds of GNSS streaming data to stationary or mobile users over the Internet, allowing simultaneous PC, Laptop, PDA, or receiver connections to a broadcasting host. It supports wireless Internet access through Mobile IP Networks like GSM, GPRS, EDGE, or UMTS.

Ntrip is implemented in three system software components: NtripClients, NtripServers and NtripCasters. The NtripCaster is the actual HTTP server program whereas NtripClient and NtripServer are acting as HTTP clients.

Ntrip is meant to be an open none-proprietary protocol. Major characteristics of Ntrip dissemination technique are:

• Based on the popular HTTP streaming standard; comparatively easy to implement when having limited client and server platform resources available.

• Application not limited to one particular plain or coded stream content; ability to distribute any kind of GNSS data.

• Potential to support mass usage; disseminating hundreds of streams simultaneously for up to thousand users possible when applying modified Internet Radio broadcasting software.

• Considering security needs; stream providers and users do not necessarily get into contact, streams often not blocked by firewalls or proxyservers protecting Local Area Networks.

• Enables streaming over any mobile IP network because of using TCP/IP.

History and Motivation

Since 1993 the RINEX Format is the standard file format for long-time storage and dissemination of GNSS receiver data, targeted mainly for the estimation of station coordinates in post-processing mode. RINEX data can be downloaded at several global and regional data centers usually as "daily" files containing 24 hours of data.
With ongoing development and the desire for getting information immediately the demand for accessing GNSS data with very small delay (in real-time) grew. Monitoring and of course positioning are probably the main use cases where real-time data is indispensable.
In order to disseminate GNSS data in real-time a new format had to be developed. RTCM messages (see RTCM Home Page) are nowadays widely used for this purpose. In addition to a format a transport protocol had to be defined, the so-called Ntrip streaming protocol, developed at BKG together with TU Dortmund. Using this protocol the data user is able to communicate with the data provider. Georg Weber, the former scientific director in the Department of Geodesy at BKG and representing BKG as a member of the RTCM Services Special Committee (SC) 104 played a decisive role in the development and promotion of real-time GNSS and Ntrip.
An important reason why Ntrip has been widely accepted is that BKG provides software tools for both, the server and the client side. On the server side the BKG Ntrip Broadcaster was developed to stream GNSS data in real-time over the Internet. The BKG Ntrip Client (BNC), which is not only an Ntrip client, is the leading internationally accepted standard Ntrip client application. It's development started in 2005 mainly by Leos Mervart from TU Prague.

Documentation

The material provided here describes the Ntrip real-time GNSS data transport protocol definition and the decodeion of an Ntrip Example Implementation. Note that the protocol definition made available here is not the official Ntrip documentation. This can only be ordered through http://www.rtcm.org.

Ntrip, Version 1.0

In September 2004 Ntrip Version 1.0 became an RTCM Recommended Standard, see Press Release.

Ntrip, Version 2.0

In June 2009 RTCM Special Committee 104 (SC104) has completed a Version 2.0 of its Ntrip standard, see Press Release. Major changes compared to Version 1.0 are:

• Cleared and fixed design problems and HTTP protocol violations

• Replaced non standard directives

• Adds chunked transfer encoding

• Improves header records

• Provides for sourcetable filtering

• Provides for Real Time Streaming Protocol (RTSP) communication

Note that Ntrip Version 2.0 is fully downward compatible with Ntrip Version 1.0.

Links to Ntrip References

The following links shall provide some background information on Ntrip usage and further Ntrip development. We try to keep the list up to date. Feel free to inform us about your Ntrip publication in case you would like to see it listed below.

Ntrip: Protocol, Video on YouTube,English
Ntrip: Client Excercise, Video on YouTube, English
Ntrip: Application and Benefit in Modern Surveying Systems, English
Nutzung der Internet-Radio-Technologie zur Übertragung von GNSS-Daten, German
Die Zukunft spricht Ntrip, German
El proyecto EUREF-IP: Resultados con GPRS, Spanish
Techniques GPS-RTK appliquées à la trajectographie, French
GNSS-Echtzeitorbitkontrolle auf Basis Internet-transferierter ..., German
D-GNSS Accuracy Test At Bucu EPN Station, English
Networked Transport of RTCM via Internet Protocol, English
Ntrip: PP-Presentation, IAG, Sapporo, Japan, 2003, English
Новый формат Ntrip передачи..., Russian
Test Results of an Internet RTK System Based on the Ntrip Protocol, English
Ntrip - Ein neues Konzept zur Übertragung von Korrekturdaten unter SAPOS, German
Benefits of Telecommunications Technology to GPS Users, English
GNSS/GPS infrastructure to support LBS Positioning Systems in Victoria, English
Ntrip Estudi i Aplicacions, Catalan
Interactive Map of EUREF-IP Real-Time GNSS Data Streams, English
Verbesserte GPS-Positionsschätzung mit IP-transportierten ..., German