I guess the followup question would be how is airport elevation determined? Student pilots are taught to compare their altimeters against the airport elevation to check the accuracy of the a altimeter and the announced air pressure. Alternatively, in the absence of a known air pressure, you are supposed to set the altimeter to that it reads out the airport’s altitude. So how is airport elevation determined? What about sloping runways (some runways run up steep mountainsides)? Are my students going to fly into the ground because no one really knows the altitude of the airport?
Yes, let us not confuse the two questions:[ol]
[li]How is elevation of a point measured?[/li][li]How is “elevation” of an extensive tract, such as a city, defined?[/li][/ol]Yes, let us not confuse the two questions:
I would go as far as to say that the great majority of sealed runway airports in the US have a surveyed elevation. It would be different for remote ranch or camp airstrips.
As for sloped runways, you need to think about the precision required to land safely on one.
This page from google (I am not a pilot!) seem to tell me that altimeters are often around 75-100 ’ out.
Since we don’t have dozens of Altimeter misreading related crashes every day, there must be enough safety margin that it doesn’t matter if the pilot comes in 20ft too low (Presumably they land closer to the runway threshold.)
I can tell you the 13th step of the state capitol building in Denver is exactly one mile above sea level. They use that as the basis for their “mile high” claim.
Hey look one I can answer! The airport is surveyed and the highest point along the runways is used as the airport elevation. Each runway end is also surveyed and that’s used as the touchdown zone elevation. The slope is calculated based upon either the ends of the runway, or depending on the length the highest point on the runway and the end.
The pilot isn’t supposed to try and land if they don’t have visual contact of the runway. Depending on the plane and speed there are given distances where you need to be able to see the runway or make a missed approach. This isn’t the case on certain approaches, but most airports and planes aren’t equipped to make those landings.
The only place I’ve ever seen a sign that says “You are now entering [name]. Population [number] Elevation [number]” in in a cartoon. Around here, the signs are small and just have the name of the town — it’s up to you to estimate the population and elevation, and to figure out that you’re entering it.
Here’s a Flickr site with a number of town signs. I see at least a few with population numbers, didn’t look that hard for elevation, or elevation and population.