1. A correction calculation method performed by a computer processor for a satellite-based positioning system including a network of receiving units as reference stations, the method comprising: partitioning the network into groups of reference stations; calculating group-specific correction variables; combining the group-specific correction variables; and deriving network-specific correction parameters, wherein during partitioning: the reference stations are represented by nodes in a cohesive, edge-weighted graph, in the generation of which the removal of the nodes connected by this edge being input into the weighting function; a minimum spanning tree is derived from the graph; and the minimum spanning tree is partitioned for establishing the groups by eliminating from a tree in each case the edge which has the highest weight and the elimination of which leads to partial trees which in each case either: satisfy a cardinality condition for the number of nodes having a lower limit n min and an upper limit n max , in both the resulting partial trees; or have a number of nodes which is greater than the cardinality condition.