Plan position indicator
From Wikipedia, the free encyclopedia
The plan position indicator (PPI), is the most common type of radar display. The radar antenna is usually represented in the center of the display, so the distance from it can be drawn as concentric circles. As the radar antenna rotates, a radial trace on the PPI sweeps in unison with it about the center point.
Usually, north is represented at the top of the image, except in the case of ship and aircraft radars, where the top represents the front part of the ship or aircraft, i.e., its heading (direction of travel) and this is usually represented by a lubber line. The signal represented is the reflectivity at only one elevation of the antenna, so it is possible to have many PPI at one time, one for each antenna elevation.
The PPI display was first used prior to the start of the Second World War in an experimental radar system outside Berlin. The first production PPI was devised at the Telecommunications Research Establishment, UK and was first introduced in the H2S radar blind-bombing system of World War II.
The PPI is used in many domains involving radars, including air traffic control, meteorology, on board ships and aircraft etc. In meteorology, a competing display system is the CAPPI (Constant Altitude Plan Position Indicator) when a multi-angles scan is available. Using computers to process data, modern sonar installations can mimic radar PPI displays too. (block diagram)
[edit] Bibliography
- Sir Bernard Lovell ECHOES OF WAR : The Story of H2S Radar ISBN 0-85274-317-3
- Adapted from Microwave Radar At War (1). There is an open source verification for this text on the home page Greg Goebel / In The Public Domain.
- A. P. Rowe: One Story of Radar - Camb Univ Press - 1948
- Dudley Saward, Bernard Lovell: A Biography - Robert Hale - 1984
- Norman Longmate The Bombers: the RAF offensive against Germany, 1939-1945, Hutchins & Co, (1983), ISBN 0091515807
- E. G. Bowen Radar Days ISBN 0-7503-0586-X
- David Atlas, Radar in Meteorology: Battan Memorial and 40th Anniversary Radar Meteorology Conference, published by American Meteorological Society, Boston, 1990, 806 pages, ISBN 0-933876-86-6, AMS Code RADMET.
- Yves Blanchard, Le radar, 1904-2004: histoire d'un siècle d'innovations techniques et opérationnelles , published by Ellipses, Paris, France, 2004 ISBN 2-7298-1802-2
- R. J. Doviak et D. S. Zrnic, Doppler Radar and Weather Observations, Academic Press. Seconde Edition, San Diego Cal., 1993 p. 562.
- Roger M. Wakimoto and Ramesh Srivastava, Radar and Atmospheric Science: A Collection of Essays in Honor of David Atlas, publié par l'American Meteorological Society, Boston, August 2003. Series: Meteorological Monograph , Volume 30, number 52, 270 pages, ISBN 1-878220-57-8; AMS Code MM52.
