pub fn track_error(
from: Position,
to: Position,
vessel: Position,
) -> Option<TrackError>Expand description
Cross-track and along-track distance of vessel relative to the great
circle leg from from to to.
Returns None when the leg has no direction to be off – from and
to are the same position, so “left or right of it” is meaningless.
Callers should treat that as “waypoint reached”, not as an error.