This page offers an overview of some key organisations in GNSS science and their relevance to the GPSdancer project. You may also be interested in the page with publications and various events of these organisations that were attended by the project. 

IAG (International Association of Geodesy)

The GPSdancer project was initiated by a working group of the IAG, called "Comparison and combination of precise satellite orbits based on different space geodetic techniques", that existed from 2004 to 2010. After completion of the term of this working group in 2010, the GPSdancer project continued independently. For formal issues, such as ownership of the Intellectual Property Rights of the GPSdancer software and its global output products, a foundation was created called the Global Geodetic Grid Foundation (GGGF).

The IAG is the parent organisation of all international geodetic services, one of which is the International GNSS Service (IGS). Others are the International Satellite Laser Ranging Service (ILRS), the International DORIS Service (IDS), the International VLBI Service (IVS), and about a dozen more.

IGS (International GNSS Service)

 

For all practical purposes, the IGS can be seen as the primary international colaboration platform for precise GNSS analysis. It produces routine global GNSS products (precise satellite orbits, satellite clocks and Earth rotation data), and station products for a few hundred reference stations in the world. All these products are generated in the form of combination solutions between the ~10 global Analysis Centres of the IGS, which has allowed all individual centres to gradually tune their analysis to near-perfect consistency with the rest of the world, in spite of the fact that each centre uses independent software, independent subsets of stations, and independent solution strategies. Associate organisations of the IGS include all major international and national space agencies, national surveys, geodetic institutions, cartographic services, and many more.

Through its bi-annual Workshops and its Working Groups on distinct technical issues, the IGS also plays a key role in the development of new models and analysis standards, and in the establishment of common file formats, formal conventions, and similar fundamental aspects of GNSS data processing. It is safe to say that without the hard work of the IGS over the past 25 years, we would not have the current accuracy and quality of GNSS processing anywhere in the world today.

IERS (International Earth Rotation and Reference Systems Service)

The IERS is a service of the IAG that routinely publishes Earth rotation information as needed in the realization of the transformation matrix between the International Celestial Reference System and the International Terrestrial Reference System. In addition, the IERS regularly publishes new releases of the formal International terrestrial reference Frame (ITRF), and series of Technical Notes that define in meticilous detail how to model various geodynamical and atmospheric effects in precise space geodetic analysis. Without the IERS we would probably still have offsets at meter level between the formal datum definition in different countries.

Needless to say that GPSdancer aims to follow the latest IERS conventions to the letter, and aims to align its own reference frame solutions exactly with the most recently published ITRF. GPSdancer does not define its own global reference frame: it wants to offer access to the existing ITRF reference frame - anywhere on Earth - with the same accuracy with which the ITRF itself is routinely realized via the IGS products.

ESA/ESOC (European Space Operations Centre)

One of the global Analysis Centres of the IGS is located at the Navigation Support Office of the European Space Operations Centre in Darmstadt, Germany, which is the ESA centre from where most European satellite missions are controlled. Because satellite operations and tracking from the ground require an accurate terrestrial reference frame, ESOC has been a founding member of the IGS and plays a leading role in its Working Groups and Governing Board.

Governance of the various IAG and IGS bodies and Working Groups is usually filled in by representatives of the various associate analysis centres and contributing organisations, and when the GPSdancer project started, the IAG Working Group that started GPSdancer was chaired by ESOC in the person of Henno Boomkamp. Because he also did most of the actual programming, GPSdancer reflects a lot of expertise gained in the IGS, notably at the IGS Analysis Centre at ESOC. A large part of the initial funding for deployment of GPSdancer in the cloud is also coming from (another part of) ESA. However, it is important to emphasize that GPSdancer is not an ESA project, but has always been a voluntary project of the IAG.

GPSdancer aims at becoming another input solution to the IGS combination products, and will to that purpose publish global GPSdancer products (orbits, satellite clocks and Earth rotation parameters) to the IGS (or to anybody else, for that matter). However, station observation data and station products (position coordinates, clocks and troposphere data) are never published by GPSdancer because they are owned by the CORS operator. For correct refrence frame collocation, it is essential that a few hundred IGS stations are included in the GPSdancer analysis, and for these stations the typical IGS products (e.g. SINEX files) can be published.

IUGG (International Union of Geodesy and Geophysics

The IAG is a constituent association of the IUGG, which forms an umbrella over most associations in the major Earth sciences such as geodesy, oceanography, meteorology, seismology and much more. It is a platform to improve collaboration and dissemination among the different sciences, because the planet Earth is a single coherent system, and none of the sciences can function properly without close interaction with the others. By cooperation in organisations like IUGG, scientific associations can optimise the use of the limited funding resources available for scientific research, while also forming an important common voice for the Earth sciences at political level.

ICSU (International Council for Science)

Naturally, there are many other sciences than the Earth sciences, and in many areas it is useful for all scientific unions to cooperate at some political level. The IUGG is therefore in turn a member organisation of the ICSU. This is a non-governmental international organisation for cooperation in science. It unites more than 30 scientific Unions and interacts with major political entities such as the United Nations. 

The relevance of ICSU to the GPSdancer system is that the world still does not have a formal political agreement on the reference frame of the planet (or the solar system for that matter), although most scientific users will use the conventional ITRS definitions. Recently, formal efforts have started to have a United Nations resolution on the formal international coordinate system, which would help to open various doors. GPSdancer can be a tool for actually bringing a single, accurate reference frame to any point on the planet, which not only illustrates the need fro some formal political agreement on the reference frame, but also makes it possible to actually have a common international reference frame.

   American Geophysical Union and European Geosciences Union

These two organisations have a similar role on different continents, namely to stimulate, motivate, organise, improve and advance the geosciences in general, not just on their own continent but basically world-wide. For most geoscientists, AGU simply means "San Francisco, early December" and EGU means "Vienna, late April" because that is where and when both organisations organise their largest annual conferences, with 24,000 participants in San Francisco (2014), and about half that many in Vienna (2015).

The key relevance of these meetings to many people in IGS or IAG Working Groups is not even the main conference with its oral sessions and poster presentations, but rather the numerous side meetings that have gradually popped-up around these conferences, in evenings or weekends. This takes advantage of the fact that many of the involved people are already collocated at one location, which avoids unnecessary traveling. It also explains why the idea for developing GPSdancer was first suggested in a bar in San Francisco.

Many technical and organisational problems were identified and/or solved during the AGU or EGU conferences. What also helps a project like GPSdancer forward, is the self-inflicted time pressure caused by submitting an abstract to a conference (...six months in advance), speaking of new milestones that are yet to be consolidated.

Project details

Ultimate Browsers SupportThe GPS Dancer project started in 2007 as a voluntary project of a working group of the International Association of Geodesy.

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Square dance algorithm

Great Docs and SupportThe GPS Dancer system was named after its "square dance" exchange algorithm. Of course, it also wants to to make the GPS reference frame denser.

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Here, there be pirates

The Dancer on-line network became immune against internet connection problems by leaving the US marines, and becoming a pirate.

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