Editing Ceilometer (section)

==Optical drum ceilometer==
An optical drum ceilometer uses [[triangulation]] to determine the height of a spot of light projected onto the base of the [[cloud]].<ref name="Lipták">{{cite book |last1=Lipták |first1=Béla G. |last2=Venczel |first2=Kriszta |title=Measurement and Safety: Volume I |date=25 November 2016 |publisher=CRC Press |isbn=978-1-4987-2766-2 |page=1570 |url=https://books.google.com/books?id=syINDgAAQBAJ&pg=PA1570 |access-date=28 December 2021 |language=en}}</ref> It consists essentially of a rotating projector, a detector, and a recorder.<ref name="Inventions">{{cite web |title=15+ Weather Forecast Instruments And Inventions That Helped Define How We Predict the Weather |url=https://interestingengineering.com/15-weather-forecast-instruments-and-inventions-that-helped-define-how-we-predict-the-weather |website=interestingengineering.com |access-date=28 December 2021 |date=23 March 2020}}</ref> The projector emits an intense beam of light above into the sky at an angle that varies with the rotation. The detector, which is located at a fixed distance from the projector, uses a [[photodetector]] pointing vertically. When it detects the projected light return from the cloud base, the instrument notes the angle and the calculation gives the height of clouds.<ref name="SKYbrary">{{cite web |title=Automated Cloud Base and Visibility Measurement |url=https://skybrary.aero/articles/automated-cloud-base-and-visibility-measurement |website=SKYbrary Aviation Safety |access-date=28 December 2021 |language=en |date=29 December 2020}}</ref>