This list becomes available if you select Best Fit or BF Recomp options when constructing the circle. It allows you to specify the type of Best Fit construction used. Available types include:
LEAST_SQR
MIN_SEP
MAX_INSC
MIN_CIRCSC
FIXED_RAD
These types are discussed below:
LEAST_SQR
Least Squares - This calculation type provides
a method of fitting in which the average squared radial distance from
the data points to the circle is minimized. The square root of this quantity
is the Root Mean Square (RMS) distance. Since the RMS distance is based
on an average, some points may be further than the RMS distance from the
computed circle.
MIN_SEP
Minimum Separation - This calculation type generates
a circle that is halfway between two concentric circles containing the
data points, with the difference of their radii as small as possible.
The Min/Max math used by the MIN_SEP calculation minimizes the maximum
error, or deviation, from the input data to the circle. The Min/Max error
is one-half of the minimal separation. No input data points (or input
features) lie farther than the Min/Max error from the Min/Max circle.
This calculation determines whether or not all the input data (or input
features) are within the given tolerances.
MAX_INSC
Maximum Inscribed - This calculation type generates
an empty circle with the largest possible diameter that lies within the
data. PC-DMIS first computes a Minimum Circumscribed circle and requires
that the center of the Maximum Inscribed circle lies within it. This option
could be used for a circular feature that requires a mating stud. For
example, if the input data represents a hole, then this calculation returns
a circle with the diameter of the largest stud that will fit inside the
hole. Do not use this calculation type for arcs of less than 90 degrees.
MIN_CIRCSC
Minimum Circumscribed - This calculation type
generates a circle with the smallest possible diameter that encloses the
input data (or input features). This option could be used when measuring
a stud that would fit into a mating circular feature. The resulting feature
would be the smallest hole into which the stud would fit. Do not use this
calculation type for arcs of less than 180 degrees.
FIXED_RAD
Fixed Radius - This calculation type creates
a circle of a given diameter, positioned so that the maximal radial distance
from the data points to the circle is minimized. It is similar to the
Max/Min math used in the MIN_SEP calculation except that, since the diameter
is known in advance, the radius cannot vary. Only the circle's position
is allowed to vary.
For legacy Circularity and Cylindricity dimensions as well as a Location dimension's RN Line, the feature solution is used to compute the dimension. By default this is Least Squares. However, you can choose to solve the feature using Minimum Separation, Maximum Inscribed, Minimum Circumscribed, or Fixed Radius regression algorithms.
FCF Circularity and Cylindricity dimensions on the other hand are computed using the Chebyshev algorithm (Min/Max) as required by the Y14.5 standard. Because of the change in calculation, Circularity and Cylindricity FCF dimensions will generally compute to a slightly smaller value than their legacy counterparts.