On Tuesday, May 15, 2018 at 3:15:06 AM UTC-4, Jim White wrote:
IGC document is an interesting read. Didn't see any reference to
calibration of barometric logger heights. The study used a vertical
encounter threshold of 15M. Most loggers are out by at least this much.

Jim

They talk about that in para 6.4:
"Other enhancements could include:
- Making use of GNSS estimated position error. Note that for vehicles close to each other, they are likely to have similar satellite visibility, subject to similar atmospheric effects, and therefore have similar position error — meaning that their relative separation erroris likely to be smaller than the position error magnitude.
- Making use of expected barometric error due to pressure sensor calibration drift and position error (variation due to cockpit interior static pressure)."