When to check that Grid Clusters remain valid Grid Groups

[richard-moulton]

Grid Clusters and Grid Groups are both defined in Chen and Tu 2007 (Definitions 3.6 and 3.4 respectively).

It is possible that a Grid Cluster could degenerate to the point where it is no longer a Grid Group and this should be checked for at some point in the adjustClustering method. Investigate whether or not to include as part of the cleanClusters method or implement separately.