OK465, inertial AOA, speed. and all that is fine in more or less still air or air that is moving horizontally - as happens "99.44%" of the time. When there is an updraft the real AOA may be somewhat different from what is indicated. And when we're speaking of single digit degrees that difference could be significant. It'd be nice to invent a real "relative to the air mass" speed and AOA measurement system. Speed's been done. AOA is an interesting problem.