Balls, you say?
On my way into work, I go over an unremarkable steel bridge. This morning, perched on the bridge’s railing, were two small white spheres like the ones in the picture. Surreal.
So I looked around and found a man in a Highways Agency van and gave him my best “what gives?” face. He held up a contraption on a tripod and said, “do you know what this is?” A theodolite, I guessed.
Not exactly. It was a 3D laser scanner and he was scanning the bridge. He had no idea why; probably for some maintenance purpose.
The spheres are a reference point. The way he explained it, the spheres can be seen from a long way off. The software knows to look for a white sphere, knows they are spheres and so can calculate the exact center as a precise reference point.
His ones were magnetic (no tripod), so he could stick them on the bridge where he liked. And very odd it looked, too. I wish I’d taken a picture, but my phone was in an inner pocket.
This site, owned by a scanning service, explains how to use multiple reference spheres to survey a large building in chunks. In their example, you use six spheres. All six spheres must be visible in each shot, but you can only move three of them at a time between images. In the end, the software can cut together an accurate picture from aligning all the references.
If you want to know more, useful search terms are “Laser Scanner Reference Sphere” or “White Sphere Scanning” (I got a lot of stupid 3D models of spheres before I found the right words).
February 10, 2022 — 8:00 pm
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