To illustrate that the pirate code can also handle combinations of anomalies that happen at different moments in a single square dance process, this example combine the two cases of Example 1 and Example 2. Node 9 was already off-line before the start of this square dance exchange, while node number 22 goes off-line in cycle 3.

As is clear from the interfering error propagation patterns in column D, a mild state of chaos exists after five exchange cycles, in which only a small subset of network nodes have found the largest possible number (namely, 31 contributions, which still includes the contributions of node 22, which is no longer on-line!). More important is that there is another group of network nodes (0 to 7) that do not have a single neighbour with a result based on more than 30 contributions. They will download this result, thinking that it is the best available, and then again compare their result with their neighbours.

Fortunately, all nodes in the range 8 to 23 will find a backup result based on 31 contributions in the first repair transaction (the first table of part E). The nodes 0 to 7, who have a result based on only 30 contributions, now all have a neighbour with a result based on 31 contributions, which is more than 30. So, nodes 0 to 7 perform a second repair transaction, and also end up with a result of 31 contributions.

This illustrates that the repair actions must be performed iteratively, until all nodes have the same result as all their neighbours.

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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