topic Re: Viewshed irregularities in ArcGIS Pro Questions

Viewshed irregularities

Oliver_Burdekin — Sun, 12 Apr 2020 15:40:02 GMT

I'm trying to find carry out a viewshed analysis but am not able to get consistent results.

Having tried and failed with viewshed and viewshed2 I discovered interactive viewshed analysis in ArcGIS Pro 2.5.0. This appeared promising but having input an observer offset of 10m and using the Ordnance Survey's 50cm DSM as the ground layer I was surprised to see the viewshed change as I zoomed the camera out (using the "C" shortcut to change the cursor to explorer mode). The ground layer uses EPSG: 27700 for the coordinate system and EPSG: 5701 for the vertical coordinate system. I'd like to know why this is happening as it makes any output from this tool unusable.

Re: Viewshed irregularities

DanPatterson_Retired — Sun, 12 Apr 2020 16:11:59 GMT

lots of options here, any particular settings you are using?

Interactive viewshed basics—ArcGIS Pro | Documentation

and at the very bottom there is this note...

Visual inaccuracies can appear as the viewshed's analysis range ratio increases.

Re: Viewshed irregularities

Oliver_Burdekin — Sun, 12 Apr 2020 16:25:37 GMT

Thanks for the quick response Dan. The settings I'm using are below:

It seems that the tool is working off the pyramids rendered rather than the actual data values.

Re: Viewshed irregularities

DanPatterson_Retired — Sun, 12 Apr 2020 16:58:21 GMT

Other than the statement, that it takes "a raster approach", there is nothing I can find, other than the exploratory videos... sorry

Exploratory analysis how-to videos—ArcGIS Pro | Documentation

Re: Viewshed irregularities

Oliver_Burdekin — Sun, 12 Apr 2020 17:46:30 GMT

Thanks for trying Dan. I'm struggling to think of a use case for a "sometimes" accurate analysis tool. Do you have any experience with the viewshed or viewshed 2 geoprocessing tools? I tried both prior to using the interactive one but had very mixed results.