Schematic, top-down representation of the GMM partitioning system. Each box represents a column of sub-partitions viewed from the top. For the highlighted sub-partition also marked with an asterisk (*), the dashed width of the box shows the region in which extra stars with a parallax uncertainty of greater than 1 mas would be included. The height of the dashed box shows the extra overlap between this sub-partition and nearby other sub-partitions. Any cluster with a centroid within the dashed region but not within the main highlighted region was automatically discarded, as it will be better characterised by the neighbouring sub-partition its centroid is in.