Viewshed Analysis
Definition
Viewshed analysis computes which areas are visible from a point or line and which observers can see a target, using terrain and optionally buildings and vegetation. It supports siting of towers, scenic overlooks, and visual impact assessment. Variants include cumulative viewsheds and visual exposure indices that count observers or visibility duration.
Application
Telecom plans line-of-sight links; parks design viewpoints; wind and solar developers assess visual impact; and defense analyzes observation and concealment.
FAQ
What assumptions can lead to overestimation of visibility?
Ignoring vegetation/buildings, Earth curvature, atmospheric refraction, and observer height leads to optimistic visibility; include these parameters where relevant.
How do cumulative viewsheds help?
They show areas visible from multiple points—useful for identifying highly exposed zones or ensuring redundancy among observation posts.
What resolution is appropriate?
Match DEM resolution to decision scale; too coarse exaggerates visibility, too fine increases cost without meaningful gain for broad studies.
How to validate a viewshed in the field?
Use photo surveys or drone reconnaissance from planned observer heights; adjust models based on discrepancies.
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