Single Spiral Dialog

A single spiral is a spiral with a beginning radius, an ending radius and a spiral length. You might enter a single spiral as part of a deed description or just insert the appropriate spiral between two existing points.

Beginning

Bearing or Azimuth - incoming bearing/azimuth. TPC inverses between the beginning point and the previous control point to determine the bearing.

Point - the traverse point that defines the beginning of the spiral.

Radius - the radius at the beginning of the spiral. If the spiral is preceded by a tangent, the radius will be zero.

Degree of Curve - alternate method of defining the radius.

End

Point - the traverse point that defines the end of the spiral.

Radius - the radius at the end of the spiral. If the spiral is followed by a tangent, the radius will be zero.

Degree of Curve - alternate method of defining the radius.

Spiral

Angle - the angle formed by tangents to the spiral at both ends of the spiral.

For a spiral with a radius at both ends,

Spiral Angle = (L/200) * (D1 + D2)

Where:

L = spiral length

D1 = degree of curve @ <Pt1>

D2 = degree of curve @ <Pt2>

Spiral Angle is in degrees

For a spiral with a radius at one end,

Spiral Angle = (L/200)D

Length - spiral length.

K - Constant of proportionality. It is rate of increase in degree of curve per station of spiral length.

= 100D/L   (L=spiral length, D=degree of curve)

Spiral Definition

This is the global spiral definition for the entire survey. Choose the Spiral Definition you want.

Direction

Choose clockwise (to the right) or counter-clockwise (to the left).

Clear

Sets the radii, spiral angle and length to zero. If you clear an existing spiral and choose OK, TPC will remove the spiral and leave the long chord in its place.

OK

Update the traverse with the spiral segment.