I was wrong about the timing - it was about 18 months ago that nincehelser posted this information in this thread:
Thanks! If I understand correctly this is only used during the learning period...or is it continuous?
Nope, that algorithm is used for all measurements. I had assumed that the AcuRite method calculated an elevation during learning mode, but that's not the case. If you look one message earlier in the thread that I posted, there's a statement clarifying this:
"The "learning method" doesn't actually estimate an elevation. It learns your average pressure through sampling for a month, then uses that average scaled against 29.92 to adjust the current absolute pressure reading.
It doesn't have any interaction with the Access. The displays use their own internal baro sensors for the calculation.
The actual equation is printed in an early 5n1 spec sheet . . ."