Viewshed & visibility analyses
A spatial data analysis and simulation conducted to evaluate the physical and visual intervisibility among specified critical elements, precisely identifying direct lines of sight and analyzing any topographical or structural obstructions.
Problem description
A spatial data-based visibility assessment (viewshed analysis) is necessary when the absence—or even the presence—of an unobstructed optical line-of-sight in physical space can generate engineering, economic, or security risks and conflicts. The core problem in every case is that, due to the complexity of the topography and the built environment, the true extent of spatial visibility (or occlusion) cannot be accurately estimated by the human eye or based on traditional 2D maps. Applications include network development and signal transmission in telecommunications; planning and pre-construction simulation of large-scale industrial and energy projects (e.g., wind farms, high-voltage transmission lines, mines); site and facility security; and real estate development.
Solution workflow
The viewshed analysis utilizes a ray-tracing approach, projecting virtual lines of sight from a designated observation point to the centroid of each target cell within the 3D elevation model. The algorithm continuously samples the model's elevation values along each projection vector. If the direct line of sight between the observer and the target cell remains unobstructed by any intervening topographical or structural features, the target cell is attributed as visible. Conversely, if the elevation value of any intermediate cell intersects the visual path, the corresponding pixel and the subsequent occluded area are assigned a 'non-visible' spatial value, effectively generating a viewshed shadow zone.
Output
The result of the simulation is typically a raster grid: single viewpoint: A binary map where cell values are assigned as 1 (visible) or 0 (occluded). Multiple viewpoints (Cumulative viewshed): The map indicates how many different observation points can simultaneously see a specific location across the area (e.g., how many cellular towers have a direct line-of-sight to a given building).
