 The Dowding system relied on a private telephone network forwarding information from the CH stations , Royal Observer Corps ( ROC ) , and pipsqueak radio direction finding ( RDF ) to a central room where the reports were plotted on a large map . This information was then telephoned to the four regional Group headquarters , who re @-@ created the map covering their area of operations . Details from these maps would then be sent to each Group 's Sectors , covering one or two main airbases , and from there to the pilots via radio . This process took time , during which the target aircraft moved . As the CH systems were only accurate to about 1 km at best , subsequent reports were scattered and could not place a target more accurately than about 5 miles ( 8 @.@ 0 km ) . This was fine for daytime interceptions ; the pilots would have normally spotted their targets within this range . 
