GNSS Data

Apr 22, 2016 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

  • Daily files, 30 sec. sampling rate (on-line for a period of 1 year) : BRUX DENT DOUR WARE

    ftp://gnss.oma.be/gnss/data/rinex/daily/

  • Hourly files :

    Each hourly file contains the data of one hour, synchronized with GPS time. Files are named as in section 4 of the RINEX specification, but with the file sequence letter "f" replaced with an hour sequence code ('A'=00:00UT to 00:59UT ... 'X' = 23:00UT to 23:59UT).

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 caster (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 caster 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 caster software can be downloaded from this website. Visit this link for more information on NTRIP.

3.2 Access

The NTRIP caster run by the ROB is available at: http://www.euref-ip.be. It is essentially a thematic EUREF relay caster, to retrieve streams once and duplicate the streams locally for further use. This decreases the load on the top casters and reduces overall internet trafic.

In order to be able to contact the streams, one has to apply for an account, by filling in the form below. By default you will get simultaneous access to 5 streams. If you need more, indicate this in the remarks field.

Please keep the password for yourself. We only need to know the hash of the password. This hash can be obtained, e.g. by the openssl passwd -crypt your_pw_in_clear command. Or you could follow this link to calculate the hash.

Your personal information is collected and stored for reasons explained in the privacy policy document.

Also please note that for the NTRIP caster the general disclaimer, terms of use, and the restrictions mentioned in the data policy document apply.

Last Name:
First Name:
Affiliation:
Address:
City:
Country Code (ISO 3166-1 alpha-3):
E-mail:
Username: (max 16 chars)
Hash of your Password:
(please no clear text passwords)
(calculate the hash for me)
Purpose, application for which
the NTRIP streams will be used:
Remarks, comments:
I grant permission to include me in the online users list
on the website of the NTRIP caster.
Please inform me by mail on (configuration) updates of the NTRIP caster.
To avoid spam abuse by internet bots, we request you
to enter the sequence shown in the image below into the box on the right.
image