Electrical Engineering/Altimeter Flight instrument.
Dear Prof Cleggsan
Do the altimeter Flight instrument indicates with accuracy the plane Altitude from the ground level to the pilot?.
How does the Altimeter Flight instrument measure the Altitude?.
Very good question.
Classically, using barometric type altimeters an accuracy of about 20 feet resolution is obtainable, I think. Smaller aircraft with medium scale instrumentation would use the basic instruments.
More sophisticated aircraft such as used in military or commercial flights may need more accuracy and more features to integrate into the overall navigation systems. Avoiding mid-air collision requires some critical instrumentation for sure.
So, there are other types of altitude measuring systems that work on radio waves or gps (satellite signals that provide very high accuracy using signals that are triangulated from several satellites traversing known orbits around the earth).
There is much science around the altimeter as modern aviation has required various levels of accuracy and integration into various levels of sophistication for applications related to the vast array of airborne vessels.
Here is a nice overview of the altimeter, its use and technology in an easy to read summarized form for getting some introduction to the many facets of the altimeter:
Next is a long discussion on the accuracy of a barometric pressure type altimeter. It explains the variations to be expected due to temperature, wind, changes due to weather, etc. It is an advanced discussion that will give you more detail than necessary, perhaps.
Next is a discussion on selecting the right altimeter for various uses and applications, pointing out the difference systems and gauges available, depending on what the user wants to do and why the altitude is important:
Here is an interesting and entertaining youtube on how altimeters work.
I am going to stop here. If you want more please send a followup question back to me.
Cheers; have a nice day.