Wikipedia says, that
a golden spiral is a logarithmic spiral whose growth factor is φ, the golden ratio.
However, other sources[only in Czech, sorry] say that the "growth factor" of a spiral is actually a scale factor of the radius after "an entire loop". (Δθ = 360°)
Using this equation (Wikipedia again) and the idea above, radius for zero angle would be 1. Makes perfect sense, doesn't it?
Radius for 2π rad (or one loop), however, would be φ4, so the ratio between the two radii (on the beginning and at the end of the loop) would be φ to the power of four instead.
Is Wikipedia wrong? Or is the used definition of growth factor?
And if so, what is the correct definition for the growth factor of a logarithmic spiral? Is it actually calculated only for π/2, or am I missing something?
As T. Bongers mentioned, the golden ratio $\varphi$ is for a quarter turn. It's apparent why when you see this image:
Credit