"Royal Air Force Radar, 1939-1945." Chain Home Low: interior of a receiver room at an AMES Type 2 CHL station. On the right are the Plan Position Indicator (PPI) and Range consoles, and in the centre is the Air Plotting Board. Early CHL stations operated similar to their larger Chain Home counterparts, measuring the range and angle to the target. These were later upgraded with plan-position indicator displays (PPI) which provide a map-like 2-dimensional view of the airspace around the station. This eliminated the need to translate range and bearing measures into positions, instead the operators could simply plot the "blips" directly on a paper map, both for record keeping as well as determining the grid locations of the targets.