GNSS Data

Sep 11, 2018 by ROB

1. Network

The ROB mountains several continuously observing GPS tracking stations. The observation data from some of the stations are freely available to the public.

2. GNSS Data for Post-Processing

GNSS stations generate data files in the RINEX (Receiver INdependent EXchange) format. The data sampling is typically 30-seconds or less. In order to minimize file size, the RINEX data are Hatanaka compressed (to uncompress Hatanaka RINEX files get the latest version from ftp://terras.gsi.go.jp/software).

The RINEX observation data can be dowloaded from

3. Real-Time GNSS Data

3.1 Format

Many proprietary formats for streaming real time GNSS corrections are in use. But to allow inter operability of receivers of different vendors in larger networks, the Radio Technical Commission for Maritime Services (RTCM) gathered a Special Commitee (SC) to define a standard for DGPS. This RTCM SC-104 standard, now at version 3, is commonly referred to as RTCM version 3. From version 2.1 onwards, the standard is also suited for RTK.

Formerly, typically the RTCM stream was transported over a radio data channel and GSM. Nowadays with GPRS, UMTS and the increase of WLAN availability, the RTCM stream can be sent over the Internet. Networked Transport of RTCM via Internet Protocol (NTRIP) can be used for this purpose.

NTRIP uses HTTP (TCP) to encapsulate a stream of GNSS data, in a way very similar to Internet radio, in order to allow transportation over the Internet.

For this, the receiver generating the GNSS data stream, called the NTRIP source, is connected to a NTRIP server (which is actually a HTTP client) that will package the serial data stream into a TCP stream. This stream will be sent to a NTRIP broadcaster (which is actually a HTTP server). NTRIP clients (again HTTP clients) can then request the stream of a certain NTRIP source, by sending a HTTP REQUEST to the NTRIP broadcaster for a certain NTRIP source, by indicating its mountpoint. If the NTRIP client does not indicate a mountpoint, the NTRIP caster replies with its sourcetable and terminates the communication.

NTRIP client, server or broadcaster software can be downloaded from this website. Visit this link for more information on NTRIP.

3.2 Access

The NTRIP broadcaster run by the ROB is essentially a thematic EUREF relay broadcaster, to retrieve streams once and duplicate the streams locally for further use. This decreases the load on the top broadcasters and reduces overall internet traffic. The ROB broadcaster is available at http://www.euref-ip.be. To register for an new account please follow the link here.