Altimeters and air pressure variation

Dean Wilkinson wrote:


Visit this website and it will answer your questions about the relationship
between pressure, temperature and altitude... altimeters are designed to
take the non-linearity into account...

http://www.lerc.nasa.gov/WWW/K-12/airplane/atmosi.html


Nice site, thanks. But presumably there is some standard
atmospheric model that altimeters use? After all nobody actually
cares whether FL300 is really 30000' feet above MSL, as
long as everyone flying there is at the same altitude and,
more importantly, not at somebody else's FL290 or FL310.

Which implies that there must be some standard mechanical
way of making the translation? I'll ask next time I visit my
avionics shop, but considering what each visit costs I
quite hope this won't be for a while.

John