This dialog displays user settings that determine how curves and spirals are defined.
Curves can be computed via Arc or Chord definition if the survey units are in feet. This option is disabled for any units other than feet.
Stationing and curve computations are based on the sum of 100' arcs if the survey units are in feet. This option is disabled for any units other than feet.
Note: To enable Curve Definition and Arc is Sum of Chords you just left click the Survey tab and select Feet for the survey units.
Spirals for the entire survey will be computed based on the spiral definition you choose here.
TPC has two methods of computing offset spirals.