measure the cone, then take an edge point on each side of the flat area inside that feature. Then construct a mid point, construct a line from cone to midpoint. Align level to cone and rotated to line. Then measure a point on each side of the radius on top of the cone making sure they are in line (section cut). construct a line and rotate to that. Measure the radius. Origin on the radius and midpoint. Then take a point straight down, Z- (0,0,1) or whatever you make that direction. Or do a scan to find lowest point.
Using small arc method, then, in the code below, replace in V1 con hits by the center of the circle defined by small arc method, then substract the radius to the distance.