EDAS is there!

EGNOS is there! Use it! I love this motto for EGNOS, the European satellite navigation system that provides integrity and improves the positioning accuracy obtained with GPS.  And it perfectly fits with what around 20 engineers at GMV have been working on since March 2012, the EDAS system. Why? Keep reading …

The EDAS system


Roughly speaking, EGNOS (European Geostationary Navigation Overlay Service) includes a network of around 40 reference stations, named RIMS. EGNOS RIMS collect GPS and EGNOS data, and send it to a Master Control Center (MCC) where EGNOS integrity and accuracy information is computed. This information is uplinked to geostationary satellites which in turn broadcast it to EGNOS users, following international standards.

But the data collected in the RIMS could be used for something else. It could actually be distributed in real time through the Internet to some “advanced” users, namely navigation-based Service Providers. They could use that data to generate added-value services for final users as, for instance, broadcasting the EGNOS messages through the Internet, instead of relying on the GEO satellite signal (which may be hidden by buildings in urban canyons, or foliage in forests). So, yes, the information was there, and it was a matter of using it!

And that is EDAS, the EGNOS Data Access Service. EDAS accesses RIMS raw data and disseminates it to authorized users through the Internet in two different formats.

The first version of the system was ready in October 2007. The service is provided since 2009 for free in a so-called beta test phase. In 2010, the EGNOS Services Provider, ESSP, started operating EDAS.

EDAS V2 and the Added Value Services

The beta test phase allowed having feedback from EDAS users and identifying new user requirements and services. Since March 2012 GMV has been working in a new version of the system, EDAS V2, which implements those new services,  which are available since April 2013.

When EDAS V1 was designed, there was no standard for the distribution of GNSS data streams over the Internet. This data distribution has become very popular in the last years and now a protocol named Ntrip is the de facto standard for that. EDAS V2 provides a new service for EGNOS RIMS GNSS data streams dissemination using Ntrip.

The SISNeT service (requested by the vast majority of users) provides the EGNOS messages through the Internet. The server allows also asking for specific EGNOS messages, satellite ephemeris and ionospheric information, allowing a faster position fix and more robust navigation solution with EGNOS.

Being really valuable and critical for some applications, real time is not a requirement for all user communities. Actually it is sometimes enough to have the data archived in an FTP site, using international and well-known standards. EDAS V2 brings this possibility by including an FTP service for GNSS and EGNOS data (e.g. RINEX observation files per station).

The former services have been adapted to the most recent version of the standards used, and enriched with a Data Filtering capability, which allows selection of the data streams on the server side according to geographical and data rate criteria.

All these services (Ntrip, SISNeT, FTP and Data Filtering) are the so-called EDAS Added Value Services.

EDAS makes a difference

The provision of added value services (on top of GNSS) requires deploying networks of stations to collect data. These networks are often geographically distributed and thus they are expensive to procure, maintain and operate. Although there are public networks that offer data following collaborative schemes, they have no warranty of service.

By the contrary, EDAS is to be provided with warranty of service (in terms of availability of data and latency). A helpdesk for user support, operated by ESSP, is also available on an H24 basis. Therefore EDAS will boost up the provision of added value services based on GNSS, as well as R&D activities related to satellite navigation.

During the development of EDAS, GMV has gained a lot of experience with the system. We have devoted significant R&D efforts to allow the integration of many of our tools with EDAS. Some success stories are:

  • magicSBAS (GMV’s implementation of an SBAS system) has been fed in real time with RIMS raw data via EDAS, in combination with local receivers in Eastern Europe, providing an EGNOS-like signal (e.g. via Internet) used in maiden EGNOS flight trials in Eastern Europe.
  • GMV’s solution for real time monitoring of GNSS performances, magicGEMINI, is able to receive data from EDAS SISNeT and Ntrip services, and post-process data retrieved from EDAS FTP. This allows a real time and off-line monitoring of the EGNOS performances over the service area, using the EGNOS RIMS as monitoring receivers.
  • EDAS data is being used by EGNOS engineers at GMV to support the evolution, maintenance and troubleshooting of the EGNOS CPF Processing Set, the subsystem in charge of computing the EGNOS corrections.

There is even more to come. EDAS is there and we will be using it!

Author: Ángel Gavín

Las opiniones vertidas por el autor son enteramente suyas y no siempre representan la opinión de GMV
The author’s views are entirely his own and may not reflect the views of GMV
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