Stacked average viewshed enhancement - a new approach to visibility analysis
Lines, John Patrick
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Visibility analysis, the determination of what is visible or not, is used in a variety of fields including real estate, civil planning, law enforcement, and spaceflight planning. Visibility can have important consequences for communities wanting to preserve skylines, law officers assessing sniper threats, or NASA planning landing sites on other planets. Geographic Information Systems (GIS) are readily used for visual assessments through viewshed and line of sight analysis. Current approaches of viewshed analysis are based on digital elevation models with each grid cell representing one height value. This single height per cell limits the ability to calculate partial visibility under tree canopies, or utility lines and features where overhanging objects obscure but do not block visibility. This thesis seeks a way to calculate partial visibility through canopied features. A new approach to visibility analysis, the Stacked Average Viewshed Enhancement (SAVE) method, creates multiple stacked viewsheds depicting partial visibility. The methodology was tested in a variety of environments, results were compared to current viewshed methods, and a SAVE toolbox was developed for use in ArcMap. This study expands the field of visibility analysis as better 3D data become more widely available.