Peter

"Joe Harrison" <newscontrol@crylo.com> wrote

>Say you are on the ground and want to measure the altitude of a plane that
>is going over your head, what (simple) equipment can you use? They are
>supposed to maintain at least 500 feet where I am but I don't believe they
>actually do. Tired of endless stream of noisy planes (helicopters the worst
>actually) when I'm pottering around in the garden.

Apart from trigonometry there is no way you can tell accurately.

If however there is say a 500ft hill (that is, a 500ft projection
**above the surrounding ground**) and you see an aircraft fly below
the top of that hill, and you are standing on the ground, then
obviously he must have been lower than 500ft above the ground.

Obviously if all ground around you is flat, there is no way you can do
this.

Many people come to a court accused of low flying, and nearly all get
acquitted, because it's easy to show that Joe Public is a very poor
judge of height.

Most fixed wing pilots will be nowhere near that low. It's hard work
flying that low and is pretty pointless. Helicopters do go lower than
fixed wing, on average.