Altimeter

[FelIX]

Ok, i have a question. How does altimeter works? I have found some that calculates the difference of air pressure from sea level. This means that everytime you must configure the altimeter to the 0 height. But this is not possible! 

Also, how does an aeroplane altimeter works? For example, if a plane travels from germany to america, the pressure is not constant. So even if the height is constant, the indication will change.
 

[Erkeli]

I do not beleive that planes use this kind of altimeter. They may calculate height with several ways like GPS or satellite. This method is for planes just cr@p

[kam]

www.thealtimeterstore.com/howtheywork.html

 

[Stefano]

Also radar altimeters. They actually measure the height not from level sea but from earth level. For planes, known landmarks or mountains can be used to calculate precise height. Eg. somewhere we know that height from sea level is 1500feet. If the radar measures another 8000feet, then this plane is at 9500 feet.

This is basically the way.

[Erkeli]

So planes must have a full combination of bar and radar altimeter plus a GPS for position. TECHNOLOGY!

[FelIX]

I think i have the picture now! Thanx

[George]

Also air pressure readings for aircraft are given by automated periodically updated broadcasts that pilots listen to

There are two types
QNA  = the local area pressure at the time period of the update period for the broadcast.

QNH = airport pressure - ie 1024mb

and aircraft are kept separated by 1000 foot levels. and the level rules change depending on the direction the aircraft if flying. One half of a circle they are on odd levels - the other half even levels.