In the CMES days, I would take the circle in question and measure 8-12 points in Polar coordinates. Then using the LP command I would extract the radius of the lowest point and place it in a real variable i.e ( PO\SG,1,12\UG,1,12\LP,Z\R1=D50 ) Then take the highest point and do the same with a different variable. i.e ( UG,1,12\HP,Z\R2=D50) Then create the variable to be used by subtracting the two i.e (R3=R1-R2) Then output the real variable as a usable point and tolerance.( X1=R3\UP,1\PT,X/\0.000,0.0001 )
Or use whatever variable you like. This always worked for me at the time.