The whole of the Tribenet world is mapped using a 26x26 grid of submaps.
Only the area outlined in red is used, with a hard border on the eastern and western edges.
Each individual submap of the grid has within it a grid of hexes, 30 across, 21 down.
Each hex is 25 miles across.
If we zoomed in to submap OM we might see this grid of hexes.
Each hex is referenced by counting along, then down.