How do modern HUDs overlay the runway? For example even the Shuttle displayed a runway outline during landing [1]. Is it just really good position determination

How do modern HUDs overlay the runway? For example even the Shuttle displayed a runway outline during landing [1]. Is it just really good position determination or is it computer vision? I assume once you're on the localiser the aircraft has a pretty good idea of the runway geometry. [1] https://m.youtube.com/watch?v=8W4cfIyNvts https://m.youtube.com/watch?v=8W4cfIyNvts