**9.4 Distance on the Surface of the Earth**

**9.4.1 Distance between Two Points Along a Great Circle**

**1.**

**A**

**nautical mile**is the length of an arc of a great circle that subtends an angle of one minute at the centre of the Earth.

**2.**The distance between two points on the surface of the earth is the arc of a circle that joins the two points.

**3.**To find the distance between two points along a meridian or the equator:

Distance of
P and Q =
( θ x 60 ) nautical miles |