The ZSA HUD is built around one question: can they see or hear me right now?
Noise meter
The bar shows how loud you are. The graph behind it shows the ambient noise around you: wind, rain, rivers. An enemy hears you only when they're inside the gap between the two. Loud weather and rushing water give you cover. See Noise.
Visibility bar
This shows how far away an enemy could spot you. Darkness, crouching, going prone and standing in cover all shrink it. See Detection & Visibility.
Enemy icons
Symbols over guards' heads show what they're thinking. The full list is on Enemy Alert States.
Compass and minimap
The compass along the top shows outpost landmarks, your pings and your Base (your claimed Bed). The minimap fills in as you explore. Zoom it with +/- or the mouse wheel.
World map
Press K for a topographic map of The Valley. It shows other players, pings, your Base, and an X where you last died. Only you can see your Base and death markers.
Clock and weather
The HUD also shows the time of day and the current weather. See Day & Night and Weather.