<DIV STYLE="text-align:Left;"><DIV><DIV><P STYLE="margin:1 1 1 0;"><SPAN>Returns polygons of visible areas for a given set of input observation points.</SPAN></P></DIV></DIV></DIV>
<DIV STYLE="text-align:Left;"><DIV><DIV><UL><LI><P><SPAN>There are several elevation sources currently available which are at different spatial resolutions and cover different areas. Not all resolutions are available for all areas. The service will return an error message if the specified resolution is not available at any of the input observer locations. </SPAN></P></LI><LI><P><SPAN>If the DEM Resolution parameter is empty or not supplied, then the coarsest resolution (90m) will be used. If FINEST is specified, then the service will use the smallest resolution available at your observer location allowed by the maximum distance parameter. </SPAN></P></LI><LI><P><SPAN>For the MaximumDistance parameter itself, 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 task 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.</SPAN></P></LI><LI><P><SPAN>The service uses a single resolution elevation source for the input features. The entire input features must fit into a single resolution, or else the service will pick the highest resolution which can cover the input features.</SPAN></P></LI><LI><P><SPAN>Visibility into water is limited, so the tool uses the water surface as the elevation service. Oceans have been assigned a value of zero and major water bodies have been assigned an appropriate flat local elevation.</SPAN></P></LI><LI><P><SPAN>The output viewshed is returned as polygon features. The field named "Frequency" is used to record the number of observation points that can see each polygon. The field named "DEMResolution" is used to record the source DEM resolution for the viewshed computation.</SPAN></P></LI><LI><P><SPAN>A lower DEM resolution will result in a faster response from the service. For example, the 90m resolution has the shortest response time from the service. The tradeoff is that a lower DEM resolution has a lower accuracy in the viewshed result compared to that of a higher DEM resolution.</SPAN></P></LI><LI><P><SPAN>The Maximum Distance parameter may also affect the Viewshed service response time. In general, using a smaller distance results in a shorter response time.</SPAN></P></LI><LI><P><SPAN>The maximum number of input points is 1000. If more input points are provided, the service will return an error and will not execute.</SPAN></P></LI></UL></DIV></DIV></DIV>
| Parameter | Explanation |
|---|---|
| InputPoints |
The point features to use as the observer locations. |
| MaximumDistance (Optional) |
The maximum distance to calculate the viewshed. |
| MaximumDistanceUnits (Optional) | <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The units for the Maximum Distance parameter. </SPAN></P><P><SPAN>The default is meters.</SPAN></P><UL><LI><P><SPAN>Meters — The units are meters. This is the default.</SPAN></P></LI><LI><P><SPAN>Kilometers — The units are kilometers.</SPAN></P></LI><LI><P><SPAN>Feet — The units are feet.</SPAN></P></LI><LI><P><SPAN>Yards — The units are yards.</SPAN></P></LI><LI><P><SPAN>Miles — The units are miles.</SPAN></P></LI></UL><P><SPAN /></P></DIV></DIV></DIV> |
| DEMResolution (Optional) | <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The approximate spatial resolution (cell size) of the source elevation data used for the calculation. The default is 90m.</SPAN></P><P><SPAN>The resolution keyword is an approximation of the spatial resolution of the digital elevation model. Many elevation sources are distributed with units of arc seconds, the keyword is an approximation in meters for easier understanding.</SPAN></P><UL><LI><P><SPAN>FINEST — The finest units available for the extent are used.</SPAN></P></LI><LI><P><SPAN>10m — The elevation source resolution is 1/3 arc second, or approximately 10 meters.</SPAN></P></LI><LI><P><SPAN>24m — The elevation source is the Airbus WorldDEM4Ortho dataset at 24 meters resolution.</SPAN></P></LI><LI><P><SPAN>30m — The elevation source resolution is 1 arc second, or approximately 30 meters.</SPAN></P></LI><LI><P><SPAN>90m — The elevation source resolution is 3 arc second, or approximately 90 meters.</SPAN></P></LI></UL></DIV></DIV></DIV> |
| 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. |
| ObserverHeightUnits (Optional) | <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The units for the Observer Height parameter. </SPAN></P><P><SPAN>The default is meters.</SPAN></P><UL><LI><P><SPAN>Meters — The units are meters. This is the default.</SPAN></P></LI><LI><P><SPAN>Kilometers — The units are kilometers.</SPAN></P></LI><LI><P><SPAN>Feet — The units are feet.</SPAN></P></LI><LI><P><SPAN>Yards — The units are yards.</SPAN></P></LI><LI><P><SPAN>Miles — The units are miles.</SPAN></P></LI></UL></DIV></DIV></DIV> |
| SurfaceOffset (Optional) |
The height above the surface of the object you are trying to see. The default value is 0. If you are trying to see buildings or wind turbines use their height here. |
| SurfaceOffsetUnits (Optional) | <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The units for the Surface Offset parameter. </SPAN></P><P><SPAN>The default is meters.</SPAN></P><UL><LI><P><SPAN>Meters — The units are meters. This is the default.</SPAN></P></LI><LI><P><SPAN>Kilometers — The units are kilometers.</SPAN></P></LI><LI><P><SPAN>Feet — The units are feet.</SPAN></P></LI><LI><P><SPAN>Yards —The units are yards.</SPAN></P></LI><LI><P><SPAN>Miles — The units are miles.</SPAN></P></LI></UL></DIV></DIV></DIV> |
| GeneralizeViewshedPolygons (Optional) | <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>Determine if the viewshed polygons are to be generalized or not.</SPAN></P><P><SPAN>The viewshed calculation is based upon a raster elevation model which creates a result with stair-stepped edges. To create a more pleasing appearance and improve performance, the default behavior is to generalize the polygons. This generalization will not change the accuracy of the result for any location more than one half of the DEM's resolution.</SPAN></P><UL><LI><P><SPAN>Checked — Generalizes the results. This is the default.</SPAN></P></LI><LI><P><SPAN>Unchecked — No generalization of the output polygons will occur.</SPAN></P></LI></UL></DIV></DIV></DIV> |
Viewshed service example (stand-alone script)
This example consumes the Viewshed service in python and save the viewshed result as a shapefile locally.
import time
import arcpy
arcpy.ImportToolbox("http://elevation.arcgis.com/arcgis/services;Tools/Elevation", "elev")
result = arcpy.Viewshed_elev(r"d:\test\testdata.gdb\sumelelvpnt1", "15000", "Meters", "FINEST")
while result.status < 4:
print result.status
time.sleep(0.2)
print "Execution Finished"
arcpy.CopyFeatures_management(result.getOutput(0), r'c:\output\viewshd1.shp')
Viewshed, Visibility, Earth and Atmosphere, Observation, Surface, Elevation, DEM, NED, SRTM
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