I just found the patent by Garmin dated 2001 and registered in 2004 where
the altitude calculation using bot a pressure sensor and a GPS is explained.
They talk about ICAO ISA reference, but maybe Ian will be helpful to explain
what's in there.
This is the link, I found it very interesting
http://www.patentstorm.us/patents/67...scription.html

Anyone can comment on this , in respect to what the IGC requires for
altitude readings?

Paul


"PCool" ha scritto nel messaggio
...

"Marc Ramsey" ha scritto nel messaggio
et...
pressure setting for a specific reporting station. There will still be
discrepancies between pressure and geometric altitude at anything other
than the elevation of the station, as the average temperature of the air
column between will almost never match that modeled by the International
Standard Atmosphere. This discrepancy can amount to over 1000 feet at
10000 feet above the station on a hot summer day...


Marc are you saying that these devices such as Garmin's S serie (baro
sensors, temperature sensor for GPS altitude corrections) can be 1000 to
10000 feet wrong?

Thanks for answering
Paul