Changes to Viewshed tool between ArcGIS 9.3 and ArcGIS 10.3

[AlexanderKeyel]

I am updating a toolbox from ArcGIS 9.3 to ArcGIS 10.x. When I run the viewshed tool (in either Spatial Analyst or in 3D analyst), I get a different result than I obtained in ArcGIS 9.3. Any idea what is causing the discrepancy? Is there any documentation regarding the tool change?

[AlexanderKeyel]

Oops - there was an error in the 10.3 results and I switched the offset & the normal values in the raster. I will try instead using the observer points approach you suggested, and see whether that fixes the problem.

[AlexanderKeyel]

Well, I don't know the exact cause of the differences, but specifying the observer elevation and offset does let me control the outputs and I can reproduce similar patterns to both what I get in 9.3 and 10.3. My guess is it has something to do with the way they are doing bilinear interpolation to get the source elevation for the default (either that or in the application of the z factor to convert from ft to m). I couldn't test it directly, because ArcGIS 9.3 kept crashing when I tried to specify the observer elevation and off-set and I've run out of time to troubleshoot it.

My take-home from this is to run a sensitivity analysis so that the results can account for some uncertainty in observer height and surface height.

[DanPatterson_Retired]

good... at least you have testing framework for assessment.  Explicit is better than implicit in any event.

You might want to close this thread so that others will know that a quasi-solution has been found.

[AlexanderKeyel]

I didn't know about the viewshed2 tool. Unfortunately, I'm not getting good results with it either! (see longer response to Dan P. above).