2006-09-02 23:11:59 · 6 answers · asked by Bhushan S 1 in Science & Mathematics ➔ Geography
It is most commonly done using barometric (air) pressure. Satellites are now used to get more accurate readings.
2006-09-03 00:04:36 · answer #1 · answered by Anonymous · 0⤊ 0⤋
There are many ways to determine the altitude above the see level
the first depends on the facts of the air that is the air is a substance so it has a weight, the weight on a unit of area is called the pressure of the air
the pressure is calculated by the following formula:
p = d*g*h
where
d is the density of the air
g is the acceleration due to gravity
h is the height of the column of the air
thus the height h can be calculated through the formula:
h = p / (d*g)
so by using barometer, which is used to measure the altitude, since both d and g are known and by applying this formula we can determine the height above sea level
In fact the rule is somehow complicated but the idea is as you see now. Best wishes
In fa
2006-09-07 02:36:04 · answer #2 · answered by waleed e 1 · 0⤊ 0⤋
First define sea level! What makes this tricky is that it varies over the Earth, depending on local gravity (yup, that changes a bit as well) and how saline the sea water is. However, once you have done that, it's relatively easy nowadays using GPS (satellite Global Positioning Systems) which, with a bit of trickery to eliminate the deliberate errors introduced by order of the US Military, to get hyper accurate readings.
All this is so much more straightforward than in days of old, when you had to survey by line of sight from a pre defined location. In the UK, the point chosen as the definitive sea level was in Newlyn, so all heights on the OS maps relate to that point in Cornwall.
2006-09-07 03:55:44 · answer #3 · answered by jjstarj 2 · 0⤊ 0⤋
It depends on visibilty and accessibility to the point. If it is visible from earth surface then it can be measured with survey system equipment (Theodolite, Total Station, etc). If it is accessible then the altitude can be measured by 'GPS survey system equipment' or Barometer.
But the above equipments have their own accuracy level.
2006-09-03 00:29:03 · answer #4 · answered by Lutfor 3 · 0⤊ 0⤋
It is measured using a really bizarre old fashioned method that triangulates the two sides of the moon from the location you want to find the height from.
If you can see how big the moon is and measure it precisely enough, you can find out how close you are to the zero...
Regards
Ichi
2006-09-04 02:51:45 · answer #5 · answered by Ichi 7 · 0⤊ 0⤋
by air pressure, as you go up it goes down
2006-09-02 23:47:58 · answer #6 · answered by allblackskikass 2 · 0⤊ 0⤋