The Blackwater–Chacewater junction area connected the Perranporth branch with Cornwall’s main-line railway. Railway records distinguish the junctions and their mileage points from Chacewater station itself.
This matters when reconstructing the line: the station, connecting curves and bridges were not a single point on a map. Road changes and the removal of railway structures have further altered the landscape. The nearby recorded Blackwater bridge is a useful historical feature, but its coordinate cannot establish the exact arrangement of the junction tracks.
Sources
Source 1: https://s-r-s.org.uk/RailRef/ref-gw.php