Talk:Radar altimeter

message: I have a question: what happens if an aircraft makes a turn, and in the process, banks? Logically, the altimeters will point sideways, and the height that they measure will increase, even to infinite when a plane banks 90° . What if the plane pulss up or dives? Are these altimeters stabilized? From what i read, most passenger jets have an altimeter to the left and one to the right. Are their different measurements used to calculate the angle of banking? And what if the terrain isn't flat? How do altimeters know wether the reading that comes from the roof of a skyscraper is the right one, or the one from the adjacent street? Are radar altimeters controlled by barometric altimeters to check for sudden and unlogical changes in altitude? This article leaves me with a lot of questions. Can sombody who knows the matter well enough provide answers to these questions please? thanks. -karelke-  —Preceding unsigned comment added by 193.190.253.150 (talk) 19:28, 4 March 2009 (UTC)
replies: text: You would only have a problem during bank if you had a very sharp (directional) beam. If the beam is wider, some part that goes, wlog, to the left as seen from the airplane, will strike the ground first, directly under the plane as seen from the ground, bounce back first, and, in the end, give a correct reading even during bank. And "sudden and unlogical changes in altitude (values shown)" do indeed happen if the terrain is not flat. As I understand it, a famous example is Funchal Airport, where the altimeter reading suddenly drops quite a bit when the airplane comes over the runway from the sea, which is quite a bit lower. (And if you bank 90° during approach, an incorrect altimeter reading will be the least of your problems.) ospalh (talk) 21:14, 7 March 2009 (UTC)
thread_title:  what if the plane banks? 

message: I don't see how this
Alternatively, the change in frequency of the wave can be measured, the greater the shift the further the distance travelled. This method can achieve much better accuracy than the aforementioned for the same outlay and radar altimeters that use frequency modulation are industry standard.
is supposed to work. Frequency changes with distance traveled? That's news to me. Could someone pleas clarify? ospalh (talk) 20:40, 7 March 2009 (UTC)
replies: text: The German page mentions FMCW, sounds reasonable, but a link would still be nice. ospalh (talk) 09:05, 8 March 2009 (UTC)

text: . Since all commercial radio altimeters in the US -- and so, I suspect, nearly all radio altimeters in general -- use FMCW, I started a section in this article about FMCW. Still needs work. I hope in the meantime the link in that section -- as ospalh suggested -- to our FMCW article gives an adequate explanation. --DavidCary (talk) 01:43, 25 January 2014 (UTC)
thread_title:  Frequency change? 

message: Please discuss the term priority of the term Radar altimeter versus the term common to aviation applications radio altimeter.  75.210.125.201 (talk) 03:15, 28 April 2013 (UTC)
thread_title:  primary term 

message: The article CLAIMS that since 2012 GPS is not suitable for altimeter measurements, and radar altimeters must be used. This statement as it stands is nonsense at least as far as guidance is concerned, a great deal of engineering effort went into establishing elevated accuracy standards for GPS altimeter accuracy in the WAAS and GBAS systems here in the United States for all manner of precision approaches, and these approaches are still on the books. There are other subsystems (GPWS?) that may use either radar altimeters or conventional air data systems with Pitot tubes, there's also the issue of which standards apply when landing at airports in non-US locations whose standards are under the auspices of the ICAO. I'm no airline pilot but as an engineer I've worked on all manner of precision avionics systems, and to state that GPS "was declared inaccurate and outlawed in 2012" is beyond absurd, and whatever system requires a functional radar altimeter would only be able to rely on it below 2500 feet anyway. It's very clear that this is way more of a political than a technical statement, at the very least the person making this statement needs to specify which subsystems ON WHICH AIRCRAFT in which context required that functional radar altimeters be added to their basic architecture for correct operation, instead of making a blanket statement which cannot possibly stand. (And it's bad enough that the FCC managed to "hold AT&T and Verizon hostage for $78 billion ransom" in order for the FAA to wage this "C band" pissing contest against the FCC, we certainly should NOT allow our government three-letter agencies to hold auctions to raise money for questionable purposes only to waste it on internecine wars!) Jlawton11 (talk) 00:27, 25 January 2022 (UTC)
thread_title:  Ambiguous about GPS altimeter issue