Navigation and Seamanship

1.2.3. Great circles

                                                                          

            A great circle is a circle formed on the surface of the earth by the intersection of a plane passing through the center of the earth, thereby dividing the earth into two equal parts.

Equator (Great circle):

            Half way between the two poles a plane perpendicular to the axis intersects the surface of the earth in a line known as the equator. Great circle is a circle on a sphere whose plane passes through the centre of the sphere. If one cuts a sphere along a great circle the plane will pass through the centre and divide the sphere into two equal halves. The plane of the equator divides the earth in half into the northern and southern hemispheres.