The .C3, .BC and .EC codes fit a curve to their respective points.
Fitting Side Shots vs Control Points
Note: In versions prior to TPC Desktop 2020 R1 (June 2020), the curve is drawn an a single ARC object in the drawing using the best-fit radius derived form the bracketed points. Beginning with TPC Desktop 2020 R1, if the respective points are control points, the curve is fitted to the existing traverse points. If the respective points are side shots, TPC still adds a single ARC object.
Fitting Side Shots
In the following example, a single arc will be drawn from point 81 to point 86 using points 81 to 86 to determine the best-fit radius..
Note .BC
81 SS
82 SS
83 SS
84 SS
85 SS
86 SS
Note .EC
Fitting Control Points
In the following example, the associated points are control points, so TPC will fit a curve of the same radius between each of the points. Points 81 through 85 will all be PCs and point 86 will be a PT.
