Jump to content
 







Main menu
   


Navigation  



Main page
Contents
Current events
Random article
About Wikipedia
Contact us
Donate
 




Contribute  



Help
Learn to edit
Community portal
Recent changes
Upload file
 








Search  

































Create account

Log in
 









Create account
 Log in
 




Pages for logged out editors learn more  



Contributions
Talk
 



















Contents

   



(Top)
 


1 Description  





2 History  





3 Uses  





4 Bibliography  





5 References  














Plan position indicator






Español
Français
Русский
کوردی
Svenska
 

Edit links
 









Article
Talk
 

















Read
Edit
View history
 








Tools
   


Actions  



Read
Edit
View history
 




General  



What links here
Related changes
Upload file
Special pages
Permanent link
Page information
Cite this page
Get shortened URL
Download QR code
Wikidata item
 




Print/export  



Download as PDF
Printable version
 
















Appearance
   

 






From Wikipedia, the free encyclopedia
 

(Redirected from Plan-position indicator)

Image of a thunderstorm line (in dBZ) seen on a 0.7-degree elevation PPI (NOAA)
Diagram showing the evolution of the height above ground, in kilometers, with the distance to the radar for the 24 PPI angles used on the Canadian weather radars (curved lines)

Aplan position indicator (PPI) is a type of radar display that represents the radar antenna in the center of the display, with the distance from it and height above ground drawn as concentric circles. As the radar antenna rotates, a radial trace on the PPI sweeps in unison with it about the center point. It is the most common type of radar display.

Description

[edit]

The radar antenna sends pulses while rotating 360 degrees around the radar site at a fixed elevation angle. It can then change angle or repeat at the same angle according to the need. Return echoes from targets are received by the antenna and processed by the receiver and the most direct display of those data is the PPI.

The height of the echoes increases with the distance to the radar, as represented in the adjacent image. This change is not a straight line but a curve as the surface of the Earth is curved and sinks below the radar horizon. For fixed-site installations, north is usually represented at the top of the image. For moving installations, such as small ship and aircraft radars, the top may represent the bow or nose of the ship or aircraft, i.e., its heading (direction of travel) and this is usually represented by a lubber line. Some systems may incorporate the input from a gyrocompass to rotate the display and once again display north as "up".

Also, the signal represented is the reflectivity at only one elevation of the antenna, so it is possible to have many PPIs at one time, one for each antenna elevation.

History

[edit]
A photograph of an 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 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.

Originally, data was displayed in real time on a cathode ray tube, 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] to this in an important way. Farnsworth refined a version of his picture tube (cathode ray tube, or 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 controllers 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.

Uses

[edit]
Simplified animation of a Plan Position Indicator radar display

The PPI is used in many domains involving display of range and positioning, especially in radars, including air traffic control, ship navigation, meteorology, on board ships and aircraft etc. PPI displays are also used to display sonar data, especially in underwater warfare. However, because the speed of sound in water is very slow compared to microwaves in air, a sonar PPI has an expanding circle that starts with each transmitted "ping" of sound. In meteorology, a competing display system is the CAPPI (Constant Altitude Plan Position Indicator) when a multi-angle scan is available.

Using computers to process data, modern sonar and lidar installations can mimic radar PPI displays too.[1]

Bibliography

[edit]

References

[edit]
  1. ^ "block diagram". Radartutorial.eu. Retrieved 2012-06-08.

Retrieved from "https://en.wikipedia.org/w/index.php?title=Plan_position_indicator&oldid=1189022970"

Categories: 
Radar
Radar meteorology
Meteorological instrumentation and equipment
Hidden categories: 
Articles with short description
Short description is different from Wikidata
All articles with unsourced statements
Articles with unsourced statements from September 2016
All articles with dead external links
Articles with dead external links from October 2023
 



This page was last edited on 9 December 2023, at 05:08 (UTC).

Text is available under the Creative Commons Attribution-ShareAlike License 4.0; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.



Privacy policy

About Wikipedia

Disclaimers

Contact Wikipedia

Code of Conduct

Developers

Statistics

Cookie statement

Mobile view



Wikimedia Foundation
Powered by MediaWiki