Hi I'm a viewshed newbie. I am working on a tower sighting project that requires me to find areas in my raster that are visible from a person's average height of 6' in my input road network (observer dataset). I am assuming the 85' towers could be in any raster cell for this purpose. For the input raster I created a normalized digital surface model. In the dropdown of this tool (observer parameters), I specify 6' in observer offset and left observer elevation blank assuming it can get elevation from the input raster. I placed 85' in the surface offset. The results showed me that all areas within my raster were visible by at least one observer. That didn't seem correct.
I then tried adding fields to my observer dataset (OFFSETA and OFFSETB) instead of populating in the tool. From the guidance, I see OFFSETA is the height of the observer so I'm assuming that's where the 6' goes and OFFSETB would be 85'. That doesn't look correct either. It seems to have been more selective (instead of selecting all areas), but when compared to the first viewshed I ran without the 85' added to the raster cells, it's less area and not more. I would expect to see more areas if the towers were an added 85' not less. Any guidance would be appreciated if I'm not thinking of this correctly. Thank you!
