Talk:Height above ground level

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Rewrote the entire page and removed the stub pointers, at least for now. Suggestions for additional information or references are welcome. Michel M Verstraete 22:47, 24 May 2007 (UTC)[reply]

Verification of CAP413 reference[edit]

Re this edit:

Quoting from source: 'Height: The vertical distance of a level, a point, or an object considered as a point measured from a specified datum (ICAO).'

Correct. Compare the definition of "altitude". If the specified datum happens to be approximately at mean sea level, height and altitude are the same, but generally they are different.

'Decision Altitude/Height In relation to the operation of an aircraft at an aerodrome means a specified altitude/height in a precision approach at which a missed approach must be initiated if the required visual reference to continue the approach to land has not been established (ANO).

It is possible to fly a precision approach referencing either height or altitude, depending on how the pilot has set the altimeter. They are not interchangeable, and there is no implication here that they are.

See also para 3.9 in the current edition of CAP413:

2.

All messages relating to an aircraft’s climb or descent to a HEIGHT or ALTITUDE employ the word ‘to’ followed immediately by the word HEIGHT or ALTITUDE. Furthermore, the initial message in any such RTF exchange will also include the appropriate QFE or QNH

This is demonstrated on the next page, with examples containing "height" when referring to QFE and "altitude" when referring to QNH. Burninthruthesky (talk) 16:20, 12 August 2015 (UTC) Paras 6.57 and 6.58 are also relevant. Burninthruthesky (talk) 16:24, 12 August 2015 (UTC)[reply]

By the way, the document we are discussing is the authoritative manual on which all UK pilots are trained and examined in order to get their radio licence. Burninthruthesky (talk) 16:41, 12 August 2015 (UTC)[reply]

I hope this clarifies any misunderstanding. In the absence of further comment in the next few days, I will remove the tag. Burninthruthesky (talk) 14:23, 13 August 2015 (UTC)[reply]

Can you please quote more explicitly where it says that, in aviation, height is reckoned from ground level, while altitude is from sea level? The source only says that QFE's datum is ground level and QNH's datum is sea level. Better if it's from an international source, e.g., ICAO. fgnievinski (talk) 03:04, 14 August 2015 (UTC)[reply]
The source does define altitude as "measured from sea level" and height as you quoted above. I have compared these definitions with ICAO Annex 10 Volume 2 and they are identical. I don't know what you are looking for? Burninthruthesky (talk) 07:35, 14 August 2015 (UTC)[reply]
Where exactly? Please quote a full sentence as given in the source. It smells WP:ORIGINALSYNTHESIS to me. fgnievinski (talk) 16:14, 14 August 2015 (UTC)[reply]
Please state what specific words in the article are not supported by the citation supplied. Burninthruthesky (talk) 08:14, 14 August 2015 (UTC)[reply]
This is the disputed sentence: In general, "altitude" refers to distance above mean sea level (MSL or AMSL), "height" refers to distance above a particular feature of the terrain. The quoted definition of height in aviation refers to an arbitrary datum, not necessarily excluding sea level as datum for height. fgnievinski (talk) 16:14, 14 August 2015 (UTC)[reply]
I take it you accept the description of "elevation" is verified? Here are the other 2 definitions (one of which you have already quoted yourself), interspersed in italics between the article's claims:
"altitude" refers to distance above mean sea level (MSL or AMSL)
Altitude: The vertical distance of a level, a point or an object considered as a point, measured from mean sea level
"height" refers to distance above a particular feature of the terrain (airport, runway, or ground at present location),
Height: The vertical distance of a level, a point, or an object considered as a point measured from a specified datum
I already gave an example above of a situation where the specified datum would be the same as sea level. It is not generally the same as sea level. What's the problem? Burninthruthesky (talk) 16:57, 14 August 2015 (UTC)[reply]
In case it helps, here is a secondary source:

[...]as a refresher, there are three standard altimeter datums:
Altitude
QNH is set on the altimeter sub-scale, and altitude above mean sea level is indicated.
Height
QFE is set on the altimeter sub-scale, and height above a set datum (usually an airfield) is indicated.
Flight level

[...]

— The Private Pilot's Licence Course, J M Pratt
This is not a controversial matter, and it is already covered in other articles (e.g. altitude.) Burninthruthesky (talk) 17:20, 14 August 2015 (UTC)[reply]
I found this in ICAO Annex 6:

Decision altitude (DA) or decision height (DH).

A specified altitude or height in the precision approach or approach with vertical guidance at which a missed approach must be initiated if the required visual reference to continue the approach has not been established.

Note 1.— Decision altitude (DA) is referenced to mean sea level and decision height (DH) is referenced to the threshold elevation.
[...]

Note 3.— For convenience where both expressions are used they may be written in the form “decision altitude/height” and abbreviated “DA/H”.

I don't think we can get much more definitive than that? Burninthruthesky (talk) 06:41, 15 August 2015 (UTC)[reply]
Indeed, the ICAO definition is pretty explicit about altitude being reckoned from sea level, thanks for that. Height, on the contrary, seems to be reckoned from pretty much anything ("specified datum" or "set datum" is left undefined in two sources above). So it seems that it's only for "decision height" that a specific datum is adopted (airfield), would you agree? fgnievinski (talk) 04:00, 19 August 2015 (UTC)[reply]
You're right that "decision height" does not define "height". It is only one example of a height which has a specific procedural meaning. The datum for "height" depends on the context in which it is used. In an approach to an airfield it would be the airfield or runway. On the other hand, if ensuring "such a height as will permit, in the event of an emergency arising, a landing to be made without undue hazard" (ICAO Rules of the Air), the height above ground level would come into consideration. Burninthruthesky (talk) 09:03, 19 August 2015 (UTC)[reply]

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