On this page, the operational performance of the Dancer network will be monitored, notably for the ITRF backbone stations. The global solution (orbits, satellite clocks, Earth rotation parameters) must be routinely monitored via comparisons against the IGS solutions, and statistics will be provided for the baselines between the ITRF reference stations, formings the key accuracy metric.

For the time being the ITRF backbone network is not yet on-line, so that there is not much to report about. However, we can show the accuracy of the Dancer software from two typical system tests, namely precise point positioning of some stations, and the accuracy of orbit fits against an external IGS final orbit, used as quasi-tracking observables. Some Figures are provided here below to illustrate this.

As soon as the ITRF backbone network is operational - even before completion of the formal validation efforts - this page will show the current status of the GPS Dancer analysis. If one day the global solution of GPS Dancer may join the IGS combination products as one of the input solutions, this page becomes redundant: the IGS Analysis Coordinater webpages provide performance summaries of the contributing solutions.

Please check back soon to see if there is any progress.

Figure 1: data volume for running a single Dancer peer, as a function of network size N. The plot dates back to 2010, but is still accurate, because the exchanged information among Dancer peers has not changed since that time. The only factor that may still influence the actual data volumes is the JXTA overhead involved with the exchange on the real internet, about which only limited performance statistics are available.


Figure 2: Required internet bandwidth for running a GPS Dancer peer. This plot can be used in combination with Figure 1 to assess the internet requirements for various solution characteristics.


Figure 3: orbit fit statistics against IGS Final orbit products. This plot was generated by fitting Dancer orbits for all GPS satellites against the precise (final) products of the IGS, over a one month period. The plot shows the error distribution, i.e. the number of comparison points (horizontal axis) that has a certain distance (vertical scale) to the IGS orbits. The plot roughly forms a Gaussian noise distribution plot, rotated by 90 degrees. The discretisation is caused by the finte resolution of the SP3 orbits that are being compared (1 mm).

The indicated 1 cm target is more or less the noise level among the various IGS input contributions, and is what Dancer hopes to achieve for the ITRF backbone network before declaring GPS Dancer fully operational.


Figure 4: Precise point-positioning statistics (RMS in mm, in east-north-up directions) over one week, for some ITRF stations. Because Dancer users are processed in exactly the same way as the reference stations, a user can expect similar accuracy levels for his own receiver.

Figure 5 a & b: observation residuals error distribution for ionosphere-free code (P3) and phase (L3). The plots show the residuals, sorted from small to large, over the PPP solutions from Figure 4. These RMS levels are very similar to what any IGS analysis centre would find.

Figure 5 Time-to-failure for various Dancer tests of the network connection stability. Solution (C) runs on a single computer. Solution (D) runs on two computers with 10 Dancer peers each (...without solving global products), connected by a public internet connection. Solution (E) runs on multiple computers on the actual internet. The typical shape of the plot indicates initially processes that do not yet work properly (time-to-failure is less than one complete Dancer run), then all at once the software is becoming stable, and can run for many consecutive square dance cycles without crashing. By Early 2013, the Dancer software was stable enough to run network solutions on the public internet. 

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.


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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