Viewshed (Ready To Use)

Summary

Returns polygons of visible areas for a given set of input observation points.

Usage

• Tools in the Ready To Use toolbox are ArcGIS Online geoprocessing services that use hosted data and analysis capabilities in ArcGIS Online.

• There are several elevation sources available that have different spatial resolution and cover different areas. Not all resolutions are available for all areas. The tool will return an error message if the specified resolution is not available at any of the input observer locations.

• If the DEM Resolution parameter is not supplied, the coarsest resolution (90m) will be used. If Finest is specified, the tool will use the highest resolution available at the observer location allowed by the Maximum Distance parameter.

• For the Maximum Distance parameter, the allowed value for the 10m and 30m DEM resolutions is 15 kilometers or less. For the 90m DEM resolution, the allowed value is 50 kilometers or less. If this parameter is not specified, the tool will use a default value based on the DEM Resolution parameter. For 10m resolution, the default maximum distance is 5 kilometers. For both the 30m and the 90m DEM resolutions, the default distance is 15 kilometers.

• The tool uses a single resolution elevation source for the input features. All of the input features must fit into a single resolution; if they don't, the tool will identify the highest resolution that will cover the input features.

• Visibility into water is limited, so the tool uses the water surface as the elevation surface. Oceans are assigned a value of zero and major water bodies are assigned an appropriate flat local elevation.

• The output viewshed is returned as polygon features. The Frequency field is used to record the number of observation points from which each polygon is visible. The DEMResolution field is used to record the source DEM resolution for the viewshed computation.

  Three additional fields are returned that identify the DEM data source used in the calculation. Those fields are Product Name, Source, and Source URL.

• A lower DEM resolution will result in a faster tool response. For example, the 90m resolution has the shortest response time. The tradeoff is that a lower DEM resolution has a lower accuracy in the viewshed result compared to that of a higher DEM resolution.

• The Maximum Distance parameter may also affect the tool response time. In general, using a smaller distance results in a shorter response time.

• The maximum number of input points is 1,000. If more than 1,000 input points are provided, the tool will return an error and will not execute.

Syntax

arcpy.agolservices.Viewshed(InputPoints, {MaximumDistance}, {MaximumDistanceUnits}, {DEMResolution}, {ObserverHeight}, {ObserverHeightUnits}, {SurfaceOffset}, {SurfaceOffsetUnits}, {GeneralizeViewshedPolygons})

Parameter	Explanation	Data Type
InputPoints	The point features to use as the observer locations.	Feature Set
MaximumDistance (Optional)	The maximum distance to calculate the viewshed.	Double
MaximumDistanceUnits (Optional)	Specifies the units for the Maximum Distance parameter. Meters —The units are meters. This is the default. Kilometers —The units are kilometers. Feet —The units are feet. Yards —The units are yards. Miles —The units are miles.	String
DEMResolution (Optional)	Specifies the approximate spatial resolution (cell size) of the source elevation data used for the calculation. The resolution keyword is an approximation of the spatial resolution of the digital elevation model. Many elevation sources are distributed in units of arc seconds; the keyword is an approximation in meters for easier understanding. FINEST —The finest units available for the extent are used. 10m —The elevation source resolution is 1/3 arc second or approximately 10 meters. 24m —The elevation source is the Airbus WorldDEM4Ortho dataset at 24 meters resolution. 30m —The elevation source resolution is 1 arc second or approximately 30 meters. 90m —The elevation source resolution is 3 arc seconds or approximately 90 meters. This is the default.	String
ObserverHeight (Optional)	The height above the surface of the observer. The default value of 1.75 meters is an average height of a person. If you are looking from an elevated location such as an observation tower or a tall building, use that height instead.	Double
ObserverHeightUnits (Optional)	Specifies the units for the Observer Height parameter. Meters —The units are meters. This is the default. Kilometers —The units are kilometers. Feet —The units are feet. Yards —The units are yards. Miles —The units are miles.	String
SurfaceOffset (Optional)	The height above the surface of the object you are viewing. The default value is 0. If you are viewing buildings or wind turbines, use their height.	Double
SurfaceOffsetUnits (Optional)	Specifies the units for the Surface Offset parameter. Meters —The units are meters. This is the default. Kilometers —The units are kilometers. Feet —The units are feet. Yards —The units are yards. Miles —The units are miles.	String
GeneralizeViewshedPolygons (Optional)	Specifies whether the viewshed polygons will be generalized. The viewshed calculation is based on a raster elevation model that creates a result with stair-stepped edges. To create a more pleasing appearance and improve performance, the default behavior generalizes the polygons. This generalization will not change the accuracy of the result for any location more than one half of the DEM resolution. True —The viewshed polygons will be generalized. This is the default. False —The viewshed polygons will not be generalized.	Boolean

Derived Output

Name	Explanation	Data Type
OutputViewshed	The output viewshed.	Feature Set

Environments

This tool does not use any geoprocessing environments.