the Evaluate Length component can be used to find the point at (and the parameter along) the curve at a certain length from the starting point. Do note that the default behaviour is for the length to be ‘normalised’, that is 0.0 = start, 0.5 = middle and 1.0 = end of curve. To use absolute length you have to set the
N input to false.
The attached file will work on any kind of curve, not just circles.
arclength.gh (10.6 KB)