Line of Sight

Line of sight (LOS) analysis evaluates the visibility between an observer point and a target point across a digital elevation model, determining whether the straight line connecting them is blocked by intervening terrain. The analysis traces a ray from the observer to the target along the surface, checking each intermediate cell to determine if its elevation rises above the ray. The result indicates whether the target is visible, and if not, which terrain features obstruct the view.

LOS analysis requires a DEM, observer location with height offset (e.g., eye level or antenna height above ground), and target location with its height offset. The algorithm interpolates the terrain elevation along the direct path between the two points, comparing the terrain profile to the straight line connecting observer and target. If any terrain point along the path rises above the line, the target is obstructed at that point. The output typically includes a visibility profile showing visible and obstructed segments along the path.

Telecommunications engineers use LOS analysis to determine whether radio signals can travel unimpeded between transmission towers, guiding tower placement and height requirements. Military planners assess battlefield visibility and weapon line of sight. Urban planners evaluate visual impact assessments for proposed buildings or infrastructure. Park managers assess scenic vista quality and identify viewpoints. Solar energy planners determine whether terrain or structures cast shadows on potential installation sites.

Line of sight evaluates visibility along a single path between two specific points, while viewshed analysisViewshed AnalysisViewshed analysis determines the areas visible from one or more observation points across a terrain surface. It is us... extends this concept to determine the total area visible from a given point in all directions. LOS is computationally simpler and is often used as a preliminary check before running full viewshed analysis.