Editing Plan position indicator (section)

== History ==
[[Image:H2S Display Cologne.jpg|thumb|left|A photograph of an [[H2S radar|H2S]] PPI display taken during an attack on [[Cologne]]. The annotations were added later for post-attack analysis. The Rhine River can clearly be seen.]]

The PPI display was first used prior to the start of the [[Second World War]] in a [[Jagdschloss radar|Jagdschloss]] experimental radar system outside [[Berlin]]. The first production PPI was devised at the [[Telecommunications Research Establishment]], [[United Kingdom|UK]] and was first introduced in the [[H2S radar]] blind-bombing system of [[World War II]].

Originally, data was displayed in real time on a [[cathode-ray tube]] (CRT), and thus the only way to store the information received was by taking a photograph of the screen.

[[Philo Taylor Farnsworth]], the American inventor of all-electronic television in September 1927, contributed{{citation needed|date=September 2016}} to this in an important way.  Farnsworth refined a version of his picture tube (CRT) and called it an "Iatron;"  generically known as a [[storage tube]].  It could store an image for milliseconds to minutes and even hours.  One version that kept an image alive about a second before fading proved to be useful for radar.  This slow-to-fade display tube was used by [[air traffic controller]]s from the very beginning of radar usage.
 
With the development of more sophisticated radar systems, it became possible to digitize data and store it in memory, allowing access at a later date.