Glossary:Contiguous grid cells

To define urban clusters and urban centres the contiguous population grid cells need to be grouped. There are two different types of contiguity.

1. Contiguous including diagonals — used for urban clusters. If the central square (grid cell) is above the density threshold, it will be grouped with each of the other surrounding eight grid cells that exceed the density threshold. This means that cells numbered 1, 2, 3, 4, 5, 6, 7 and 8 can be included in the same cluster.
2. Contiguous excluding diagonals — used for high-density clusters. If the central square is above the density threshold, it will be grouped with each of the four cells directly above, below or next to the central square that also exceed the density threshold. This means that cells numbered 2, 4, 5 and 7 can be included in the same cluster. Cells with numbers 1, 3, 6 and 8 cannot as they have only a diagonal connection.