Mach asked how to do the correction in starting this thread and I guess he got his answer. Some good stuff was sent in.
I pointed out that modern airplanes may not need to be corrected because the CADC/(ADIRU) Altimeter reading is already corrected.
I flew in a 747-400 last week and noted the altimeters: One is from the ADIRU and the other is a (standby) Pressure Altimeter. On the ground, with the same altimeter setting and in the same airplane, I saw that at ISA minus 15 the Pressure Alt was overreading the main Alt by 25 feet. At minus 10 it was overreading by 5 feet, and at plus 15 it was underreading by 25 feet.
(In the air the differences are obscured by Position Error, quite severe in the B744.)
This is double what I would have expected so there could very well be other factors, but it tends to support the Boeing and Honeywell Technical Manuals.