[djsavvy]

A sibling comment to yours asked about the elevation --- apparently it's actually a measure of air pressure.

[speedgoose]

That's strange that they use such an inaccurate sensor when they have a GPS.

[djsavvy]

Apparently the reasoning is that what actually matters is oxygen partial pressure in the atmosphere, not true elevation. Measuring air pressure and reporting as elevation is a decent proxy for what athletes actually care about.