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How do I 'describe' this simply trigonometric relationship?

I'm interested in the decreasing angles between objects at increasing distance from the viewer, as attached.

I know that the the angle is the arctan of the opposite / adjacent. This is basic high school SOH CAH TOA.

But how do I describe this relationship in text form? I'm interested in the way that distant things in the horizon appear more and more clumped together, because the more distant things are, the less 'vertical angle' from the observer they get to share.

So I might say something like the "vertical angle of features decreases with the arctangent of distance over height" but that sounds wrong. How would I express this simply trigonometric concept elegantly?

The specific example I'm looking at is mountains. When you stand on a high mountain the foreground appears large, but as you look higher and higher towards the horizon things get more and more squished together. Let's ignore earth curvature here for the moment! If anyone can help with the wording I'd be grateful. Thanks

http://www.mathhelpforum.com/math-he...p-stickman.jpg

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