lineofsight

Line of sight (LOS) is the unobstructed line between an observer and a target along which light or signals travel. It is a geometric concept used across optics, vision, surveying, and communications to describe whether a direct path exists between two points.

In human vision, LOS refers to the direct path along which light travels from an object to the eye. It determines what is visible at a given moment and is limited by physical obstructions, atmospheric conditions, and scattering. Even when a direct path exists, slight atmospheric effects can influence perceived clarity.

In optical and radio communications, LOS denotes a straight, unobstructed path between transmitter and receiver. For reliable performance, the path should be free of major blockages, and the distance can be limited by the curvature of the Earth. Atmospheric refraction, weather, and terrain can extend or reduce effective LOS. In practice, signals may still reach beyond strict LOS via diffraction, reflection, or atmospheric ducting, but such non-LOS propagation often degrades quality. The Fresnel zone concept is used to assess potential obstructions near the LOS that can affect signal strength.

In surveying and navigation, LOS observations are essential for accurate measurements, as instruments require a clear sightline to target markers or celestial bodies.

In gaming and simulation, LOS is used to determine visibility and line-of-fire. Algorithms typically perform ray casting or voxel checks to decide whether a character can see another entity, with walls and other obstacles blocking sight.