We live in a 3D world, but we still use paper and screen to learn. So our brain is used to analyze in 2D.

Often, when someone wants to observe and analyze a motion, the horizontal point of view is chosen. This choice is simply the natural way for humans to see the world. The results are understandable and often clarifying.

Nevertheless projecting ourselves in another frame of reference is a very enchanting way of observing the world. In the introduction, I wrote about 2D and 3D. In this case, what would happen if we start observing someone from the Y axis of the following picture?

We would mostly see his head and shoulders. Now if he starts walking? We would see his shoulder line, pivoting at the opposite of his hip line, like this:

The pivot points are at the vertical of the head and the spine.

It is very rare to observe motion this way. But it is so useful in order to measure issues regarding symmetry, synchronicity, regularity...

That is also a reason why humanoid robots often don't walk like us. Their shoulders and hip lines are rigid.

Next time you take a walk, what about picturing your gait from the sky?