0

This question seeks to clarify a point made in an answer to ArcGIS Viewshed without Observer Points, which states:

I'm fairly sure that the number of points [Viewshed] generates along the line depends on the DEM resolution; for example, if you've got a 100m line and a raster with 10m cells, your line will be analyzed as 10 points.

Can anyone confirm this is true in ArcGIS Pro? I have a DEM raster of 30-meter cell size, and a polyline observer feature that is quite long (a 463 kilometer boundary line to be precise.) I'm getting a maximum of 279 observers. When you work out the math that would mean ≤2% of the boundary can "see" any given cell. It seems too low.

(Specifically I'm looking to convert the number of observers into the percentage of the boundary.)

2
  • 1
    Have you reviewed Using Viewshed and Observer Points for visibility analysis and other ArcGIS Pro help pages about the Viewshed tool and Viewshed function? – PolyGeo Nov 19 '20 at 1:47
  • @PolyGeo I had, but apparently missed this useful bit: "When polyline input is used, every node and vertex along each input arc is processed as an individual observation point." Now I suppose I just need to determine how to count the number of nodes and vertices. – D. Betchkal Nov 19 '20 at 1:54
0

One (awkward) answer:

When using polyline inputs to the Viewshed tool, one can use arcpy.management.FeatureVerticesToPoints("polyline feature", "output point feature", "ALL") to convert every vertex to a point. Then the length of the attribute table provides the number of observer points.

In the case of this question, it gives a much more reasonable value of 957 observers. Or, the most visible cell in the DEM raster was visible from ≤29% of observer points.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.