CAD/D Home > MicroStation > Spiral Curve Data

This document shows
the way that spiral curve data should be shown on Highway Design plans and
briefly describes the meaning of each item listed. For more information,
see Drafting Spiral Curves From Old Plan Data.

Sample Curve Data

Detail in leading spiral curve area.

New Hampshire Department of Transportation

PO Box 483 | 7 Hazen Drive | Concord, NH | 03302-0483

Tel: 603.271.3734 | Fax: 603.271.3914

Sample Curve Data

Detail in leading spiral curve area.

PI= 23+96.20 | PI | Station of intersection point of start and end tangents |

N = 405083.92 | N | North coordinate |

E = 964724.93 | E | East coordinate |

Δ = 77°-47'-44.8" RT | Δ | Angle between start and end tangents |

Δc = 39°-35'-54.9" RT | Δc | Angle turned by the circular portion of the curve |

Dc = 19°-05'-54.9" | Dc | Degree of curve on Imperial alignments |

Ts = 346.15' | Ts | Distance from tangent point to intersection of tangents |

Es = 92.58' | Es | Distance from PI point to curve |

Ls = 200.00' | Ls | Length of spiral |

Lc = 207.34' | Lc | Length of circular portion of curve |

Rc = 30 0.00' | Rc | Radius of circular curve |

LT = 134.12' | LT | 'Long Tangent' of spiral curve |

ST = 67.38' | ST | 'Short Tangent' of spiral curve |

θs = 19°-05'-54.9" | θs | Angle turned by spiral portion of curve |

P = 5.53' | P | Offset of circular curve from tangent line at the point where the circular curve would be parallel to the tangent if it were extended. |

K = 99.63' | K | Distance along the tangent to the point described immediately above (marginally less than half the length of the spiral) |

Xc = 197.79' | Xc | Distance along tangent from point of tangency to end of circular curve |

Yc = 22.05' | Yc | Distance perpendicular to tangent from tangent line to end of circular curve |

LC = 199.01' | LC | 'Long Chord' distance between ends of the spiral |

New Hampshire Department of Transportation

PO Box 483 | 7 Hazen Drive | Concord, NH | 03302-0483

Tel: 603.271.3734 | Fax: 603.271.3914