Choose a reference
An object whose height you know, placed in the same perspective.
Similar triangles
Find a height
without measuring it.
Compare two triangles in a Thales configuration: one known height is enough to deduce the inaccessible.
Quick calculation
Your measurements
01
H₁d₁
H₂ ?d₂
Same angle · proportions preserved
In 3 steps
The principle, simply.
Measure both bases
Note d₁ for the reference and d₂ for the target height.
Let Thales conclude
Similar triangles maintain the same proportion: H₁/d₁ = H₂/d₂.