What is the significance of a 'decision altitude' (DA) or 'decision height' (DH)?

The significance of a 'decision altitude' (DA) or 'decision height' (DH) is that it represents a critical point during an instrument approach where the pilot must make a decision regarding the continuation of the descent toward landing or the initiation of a go-around. At this specific altitude or height, the pilot must have visual reference to the runway or the required navigation aids to determine whether it is safe to land.

If the required visual references are not in sight at or before reaching this altitude, the pilot must execute a go-around procedure to ensure safety. This decision point is essential for maintaining safety during low-visibility operations and helps prevent landing accidents due to insufficient visual cues. Thus, understanding decision altitude or height is crucial for pilots in ensuring they make informed decisions based on the visual conditions at the time of approach.