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### 1. Circle; Arc

Figure D-1 is a diagram of a circle and Equation D-1 is its equation in terms of North and East coordinates.

Figure D-1 Circle |

Equation D-1 | ||

where: | ||

O |
radius point point on circumference radius |

An arc is a portion of a circle, Figure D-2.

Figure D-2 |

Generally we only need an arc long enough to meet an intersection condition. We'll cover other specific arc geometry in the *Curvilinear Traverse* chapter.