Just look at the VERTICAL intersections through the arcs. Where the VERTICALS intersect is why the angle stopped there.. and some angles hang in mid air or mid channel.
This idea is like squares with the arcs intersecting the squares. The problem is every chart has specific arc distances and angles speeds. I find the best results are by first finding ellipses that hit at least 2 points on the same arc, then from the same ellipse center I try for other distances where there are multiple hits on a larger arc. Once I find consistency in points hitting multiple arc distances ALL from the SAME CENTER point. Then I rescale the chart into a circle. The projection tool can be overlaid to see if the circle has the proper circular shape.
Once everything is in order. The Fib can be used. They always draw a perfect arc. Just clone the arc sizing to reuse it elsewhere.
An easy way to set this up would probably be to find the right arc distance, then draw a horizontal on the chart, the same as the arc distance as a reference point. Just lay the fib over the horizontal line and it's specific distance to reuse the arc distance.
So you have 3 correlations to help find a possible reversal point. 1. The channel distance across (the channel angle should have a lead point to set it's angle 1st). 2. Common angle speeds that reoccur across the chart ( there are usually only 2 or 3 main angle speeds) 3. Arc distances (stick to the sizing that is closer to the move you are looking at). Although I do look to see if other distances from a center also line up.
If everything worked out...and you're lucky and have good sense of general direction and angle speed, then it's possible to nail the point.
I did this on EURCAD mostly with the channel sizing. The angle was off, but the channel height was right. On the other hand coming down, my arc distance was right, the channel distance right, but the speed was off. I missed the top by 6 pips and the bottom by 45 pips.
Now don't expect THAT one every time, but I think these correlations between angles, arcs, and channel sizes help the accuracy.