Editing Altimeter (section)

=== Radar altimeter ===
{{main|Radar altimeter}}
[[File:Cockpit of Piper PA-28-151 (G-BOYH) at Bristol Airport, England 15May2016 arp.jpg|thumb|The altimeter on this [[Piper PA-28]] is seen on the top row of instruments, second from right]]
A [[radar altimeter]] measures altitude more directly, using the time taken for a radio signal to reflect from the surface back to the aircraft. Alternatively, Frequency Modulated Continuous-wave radar can be used. The greater the frequency shift the further the distance travelled. This method can achieve much better accuracy than the pulsed radar for the same outlay and radar altimeters that use frequency modulation are industry standard. The radar altimeter is used to measure height above ground level during landing in commercial and military aircraft. Radar altimeters are also a component of terrain avoidance warning systems, warning the pilot if the aircraft is flying too low, or if there is rising terrain ahead. Radar altimeter technology is also used in [[terrain-following radar]] allowing [[combat aircraft]] to fly at very low height above the terrain.

After extensive research and experimentation, it has been shown that "phase radio-altimeters" are most suitable for [[ground effect vehicle]]s, as compared to laser, isotropic or ultrasonic altimeters.<ref>
Nebylov, Prof. Alexander and Sharan Sukrit.
"Comparative Analysis Of Design Variants For Low Altitude Flight Parameters Measuring System".
''17th IFAC Symposium for Automatic Control.''
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