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The Post Plotting Instrument, or simply Post Instrument, was the standard optical sighting system used by the UK's Royal Observer Corps (ROC) to determine the location of aircraft. It was used during the period from the mid-1930s into the early 1950s, and was one of the main sources of daytime tracking information during World War II. There were two versions of the Post Instrument, a pre-war model using a pantograph, and a wartime version of somewhat more sophistication. Both required the operator to estimate the altitude of the aircraft and enter that into the device, then point an mechanical indicator, or sight, at the aircraft. The motion of the sight moved an indicator on a small Ordnance Survey National Grid map. The grid location indicated by the pointer was then telephoned to central control rooms, where several such reports were combined to produce a more accurate location estimate. Later models added the Micklethwait Height Corrector, which allowed the posts to measure altitude with some accuracy and thus improve the quality of the measurements. The ROC also developed a methodology that allowed the Post Instrument to be used to produce measurements purely by sound, but it is unclear how often this was used. ==Background== Prior to the introduction of radar, optical tracking systems of widely varying complexity were commonly used to spot and report aircraft positions. The Post Instrument was intended to be at the simple end of the scale, an inexpensive and easy to use instrument to make rough but rapid measurements of the locations of aircraft. Post Instruments were installed at hundreds of observation posts across the UK, typically in small groups of three or four posts about apart. This spacing allowed the operators to cross check each other's altitude measurements. Each post was normally manned by two or three operators, one operating the Post Instrument, another using the telephone to report the locations to a plotting center, and the third, if present, operating as a lookout and helper. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Post Instrument」の詳細全文を読む スポンサード リンク
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