Heh, true. I deliberately left out altitude because this is HN but you caught me anyway.

Presumably a train's groundSpeed and airSpeed are the same. If they diverge you have bigger problems than a JSON schema.

Is there a variant of this for ships? surfaceSpeed vs seaFloorSpeed?

A train can easily run in a head- or tailwind in the same order of magnitude as its groundspeed.

I've been tempted to mount a small anemometer to my car - by subtracting the groundspeed from the measured airspeed, one can get the wind speed and direction and figure out whether there is a headwind or tailwind and if so how strong. Theoretically this could be used to drive more efficiently, though the extra drag from the anemometer would probably cancel out any gains.

Wow I got HN’ed twice in one thread. This is not my day.

Well, ships have apparent wind vs real wind and apparent course vs real course (currents and drift are a thing).