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Plotters were employed on an early form of air traffic monitoring that played a vital role in World War II, particularly during the Battle of Britain, The Blitz and the bombing of British cities that followed. They worked at individual RAF stations' Sector Control Rooms or in the central Group Control Rooms that directed the operations of RAF fighters. The majority of plotters were female, members of the Women's Auxiliary Air Force (WAAFs).
Plotting depended on reports from the newly installed Chain Home radar stations that detected aircraft approaching the coastline, and the Royal Observer Corps posts that spotted hostile and friendly aircraft over land.
Such reports were fed to a Filter Room, where Filter Plotters processed the mass of incoming data by hand and fed a digest to the underground Operations (Ops) room. There, information about aircraft movements was passed to a large number of plotters stationed around a giant table bearing a map of the section. Details about the number of aircraft, their position, height and bearings were transferred to counters that were positioned and moved around the map by the plotters, in a similar way to a croupier at a roulette table, using plotting rods that were adjustable in length and magnetised to pick up the plots.
Each plotter was responsible for aircraft movements in a particular sector, changing the plots regularly so that the whole picture of a raid could be monitored by the Group controllers who were stationed in a gallery above the plotting table.