#### Best Fit Type

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

- MAX_INSC

- MIN_CIRCSC

- MIN_SEP

- FIXED_RAD

These types are discussed in the table below:

List Item | Description
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.
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.
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 Chebychev 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.