Create Viewshed
The Create Viewshed tool creates areas where an observer can see objects on the ground. The input observer points can represent either observers (such as people on the ground or lookouts in a fire tower) or observed objects (such as wind turbines, water towers, vehicles, or other people). The result areas are those areas where the observers can see the observed objects and vice versa: the observed objects can see the observers.
Both the observers and the observed objects can have a height above ground, and these heights are used in determining visibility. For example, a viewshed computed for 400-foot wind turbines and six-foot people standing on the ground will typically be larger than a viewshed computed for 200-foot turbines and six-foot people.
Note that the computation of the viewshed does not account for obstructions such as trees or buildings. You can think of the computation as occurring on bare ground devoid of anything but the observer and observed objects.
The result layer contains area features representing visible areas. The Frequency field records the number of observer points that can see each area. For example, if you have five input points, each representing a fire lookout tower, the Frequency field will have values between one and five; areas with a value of one can only be seen by one tower, and areas with a value of five can be seen by all towers. The result layer also contains the DEMResolution field, which records the resolution of the digital elevation model (DEM) used to create the viewsheds.
If Use current map extent is checked, only the observer points that are visible within the current map extent will be analyzed. If unchecked, all observer points in the input layer will be analyzed, even if they are outside the current map extent.
elevationSurface
The elevation surface.
Point features that represent observer locations
The point features to use as the observer locations.
Optimize for
The optimization method.
- Accuracy — The method for creating viewsheds is optimized for accuracty in the results, at the expense of a longer processing time. This is the default method.
- Speed — The method used to calculate the viewshed is optimized for speed, trading some accuracy in the result for higher performance.
Maximum viewing distance
This is a cutoff distance where the computation of visible areas stops. Beyond this distance, it is unknown whether the observer points and the other objects can see each other.
Maximum viewing distance
This is a field you can use to specify the maximum viewing distance for each observer.
Minimum viewing distance
This is a distance where the computation of visible areas begins.
Minimum viewing distance
This is a field you can use to specify the minimum viewing distance for each observer.
Distance in 3D
You can define whether the distance in measured in true three-dimensionals or a simpler, two-dimensional way.
When the option is checked, the viewing distance is calculated in 3D units. When it is unchecked, is it calculated in 2D units.
Elevation of observer locations
This is the elevation of your observer locations.
Elevation of observer locations
This is a field you can use to specify the elevation for the observers.
Height of observers
This is the height above ground of your observer locations. The default is approximately the average height of a person.
Height of observers
This is a field you can use to specify the elevation for the observers.
Height of target
This is the height of structures or people on the ground used to establish visibility. The result viewshed are those areas where an observer point can see these other objects. The converse is also true; the other objects can see an observer point.
Height of observers
This is a field you can use to specify the elevation for the targets.
Output height to become visible
The output above ground level (AGL) raster.
Result layer name
This is the name of the layer that will be created in My Content and added to the map. The default name is based on the tool name and the input layer name. If the layer already exists, you will be asked to provide another name.
Using the Save result in drop-down box, you can specify the name of a folder in My Content where the result will be saved.