Mathematical Problem

[Freaki Li Cuatre]

I need to produce a photo montage showing what a proposed structure will look like in relation to its surroundings (It's a chimney at a nearby cement works as it happens)

I know the height of the chimney. I have a photo taken at a known distance from the site of the chimney.

How do I work out what size to make the chimney in my montage?

[sasguru]

SOHCAHTOA

[RedSauce]

SOHCAHTOA

Not without knowing the angle

[SimonMac]

SOHCAHTOA

Over complicating it.

Just work out the ratio of the known height and the photos height and apply the same ration to the new structure in the montage

[minestrone]

forget that

[CheeseSlice]

Google 'perspective', although you can probably find some rules of thumb that make some broad assumptions.

[russell]

I need to produce a photo montage showing what a proposed structure will look like in relation to its surroundings (It's a chimney at a nearby cement works as it happens)

I know the height of the chimney. I have a photo taken at a known distance from the site of the chimney.

How do I work out what size to make the chimney in my montage?

You know the opposite (height) and the adjacent (distance) now find the hypotenuses using Pythagoras theorem. Then scale it down keeping the same ratios of sides.

[SimonMac]

Not without knowing the angle

The angle can be worked out using Pythagorean theorem

[sasguru]

The angle can be worked out using Pythagorean theorem

tan(angle)=opp/adj.

[RedSauce]

tan(angle)=opp/adj.

But you are assuming that it is a right angled triangle with the photo being taken level with the base of the chimney.