Summary GenNav - Great Circles

Great Circle Vertices


Northern
Vertex 63N
Crossing Great Circle 010E
Point
(100E)




Equator 63




Southern Vertex
(63S 170W) Crossing
Point (080W)




S. Vertex (170W)
Northern and Southern Vertices of a great circle are the most
Equator Crossing northerly and southerly points on that great circle.
The vertices are ANTIPODAL (opposite) in terms of latitude
and 180 degrees apart in longitudinal terms.
North Pole Eg. 63°N 010°E and 63°S 170°W
100E At either vertex the track direction is either 090° or 270°

080W A Great Circle crosses the equator at two points where the
longitude is 90° removed from either of the vertices.

From the example here, the crossing points will be 100°E
and 080°W
N. Vertex First Crossing (Tracking East)
North
N. Vertex At either vertex the track direction is 090° or 270°.

The track direction when crossing the equator will
be at an angle equal to the latitude of the vertices.
90
From this example, if heading east from the
Equator northerly vertex the angle of the track direction will
be 090° + 63° = 153° when first crossing the
63 equator.




S. Vertex

090 + 63 = 153
degrees