Viewshed Analysis:Comparative Development of Eastside and Westside Hills in the Portland Metro Area
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Viewshed analysis has been around for a long time and has various uses. A few examples of uses are cell tower locations, building site locations, real estate values, and archeology. Two main types of visibility models used are line-of-sight and viewshed. Line-of-sight profiles model point to point visibility, while viewsheds model point-to-area visibility. (Analysis and Visualization of Visibility Surfaces, 2003) Viewshed analysis is used to calculate which locations in a digital elevation model (DEM) can be connected by an uninterrupted straight line to a viewpoint location within any specified distance. (Llobera, 2003)
Using multiple viewsheds and combining them to create a cumulative viewshed is commonly used
A view where the focus of the analysis is on understanding the relationship between points in isolation, and where concern about space in-between is lost and deemed meaningless and inert. (Llobera, 2003) Cumulative viewsheds can be used to identify where the visual presence of features may be greatest. (Llobera, 2003)
My Idea was to determine the visibility of development of hillsides as looking at it from the valley floor and compare Eastside and Westside hills. Using small cumulative viewsheds I can try to determine where the visual presence of houses may be greatest.
The model “viewshed” in Idrisi it creates a 360 degree arc around the point or area of the viewpoint and calculates which cells from the surface image are visible within the specified distance. Creating a continuous viewshed of the area involved would be time prohibitive, not practical for the purpose of this project
Data and sources:
Taxlots, zoning, and vegetation shapefiles are from RLIS data and Oregon10m DEM N fro...
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...of undeveloped areas.
I gained a better understanding of the viewsheds and their complexity and a better knowledge of Irdisi’s processes. Error that happened: reclass sum files ended up the same for trees and without trees which gave me the same results and I needed to go back and redo the analysis.
I gained a better understanding of the viewsheds and their complexity and a better knowledge of Irdisi’s processes.
Analysis and Visualization of Visibility Surfaces. Caldwell, D.R., et al. 2003. 2003.
Joly, Daniel, et al. 2009. A Quantitative Approach to the Visual Evaluation of Landscape. Annals of the Association of American Geographers. 2009, Vol. 99, 2, pp. 292–308.
Llobera, M. 2003. Extending GIS-based visual analysis: the concept of visualscapes. International Journal of Geographical Information Science. 2003, Vol. 17, 1, pp. 25-48.