In Figure 1-3, the geodetic latitude of point P has been formed by the angle of the semimajor axis and a
perpendicular (or plumb) from point P on the edge of the ellipse. The geodetic longitude of point P has
been formed by the angle between the plane of the Greenwich meridian and the meridian plane of point
P.
Figure 1-3. Geodetic Coordinates
d. Defining the Earth's Equator. For years, scientists have discussed the possibility that the earth's
equator is an ellipse rather than a circle and, therefore, that the ellipsoid is triaxial. Until recently, the
study has been slowed due to insufficient data. Modern technological developments have furnished new
and rapid methods for data collection, and since the launching of the first Russian sputnik, orbital data
has been used to investigate the theory of ellipticity. However, it will be some time, even at today's rate
of data collection, before an exact conclusion is made.
e. A Second Theory. A second, more complicated theory than triaxiality proposes that satellite
orbital variations indicate additional flattening at the south pole, accompanied by a bulge of the same
degree at the north pole. It is also argued that the northern middle latitudes are slightly flattened, and the
southern middle latitudes are bulged in a similar amount. This new concept suggests a slightly pear-
shaped earth and has been the subject of much discussion.
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