Today a friend of mine made me realize that roundabouts have “perfect” road markings around them and i started wandering how a machine would go about making a circle without a compass-like system. So i tried google but every result led to either a janky home made compass or some sort of hand-drawing technique. I assume it should be possible to draw a circle knowing the radius in an analog system without a compass but i can’t figure out how. Plus i don’t know how the physical structure of a roundabout is made to be round and that is even weirder to think about.
TLDR: How are roundabouts and round road markings made?
For the markings, I’ve seen such a small cart that just had an adjustable wheel on a pole at the side. Since the pole was fixed length, they just kept the wheel near the outer road border and thus kept the distance always the same, keeping the marking in the middle.