page_title: Viewshed analysis
section_title: A unique viewshed analysis
hierarchical_section_title: Viewshed analysis / A unique viewshed analysis
caption_attribution_description: English: Viewshed of MER Project landing site "Gusev Crater" overlaid on an elevation map
context_page_description: A viewshed is an area that is visible from a specific location. Viewshed analyses are a common function of most geographic information system software. The analysis uses the elevation value of each cell of the digital elevation model to determine visibility to or from a particular cell. The location of this particular cell varies depending on the needs of the analysis.
  For example, a viewshed analysis is commonly used to locate communication towers or determining the view from a road. Viewsheds can be calculated using an individual point such as a tower or multiple points such as a line representing a road. When analyzing a line segment, each of the vertices along the line is calculated to determine its visible area. The process can also be reversed. For example, when locating a landfill, the analysis can determine from where the landfill is visible to keep it hidden from view.
context_section_description: In another example the United States Geological Survey (USGS) used a viewshed analysis to assist NASA's Mars Exploration Rover (MER) project. When NASA needed to find appropriate landing spots for the Mars rovers, they turned to the USGS to map the best possible sites. Part of the analysis included a viewshed of the possible site selections. In this case the viewshed indicates the areas which may or may not be visible by the Mars rovers from each landing site (MER Landing Site Viewshed Analysis).
caption: Gusev crater on Mars: the viewshed (red) is overlaid on an elevation map
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