# Calculating the perceived size of an object as part of a viewshed analysis

I am conducting a visibility analysis on a radio station tower. I want to know how big the viewers across the area will see it. For example, those further away will perceive the tower to be smaller.

If the tower is 30 metres tall and I know the distance of the observer to the tower, is there a way to calculate the size the observer will perceive the tower to be?

This is in ArcGIS Pro.

• That's not how the Viewshed command works (it calculates what can be seen from a point or points across a surface). Commented Oct 21, 2022 at 21:17
• @Vince yes I know that, I should have not used viewshed in the question. I am doing a visibility assessment so seeing if people can see the mast Commented Oct 22, 2022 at 6:48
• You can use basic trigonometry to determine how many degrees tall the object will be, but you also need to consider the thickness, and whether hills, trees and structures will occlude the tower (which Viewshed could calculate, with sufficient information, which isn't easy to obtain) Commented Oct 22, 2022 at 13:32