Position P
would appear to represent an aircraft in flight above the surface of the earth.
The perpendicular right angle is not where line from the centre of the earth
cuts the geocentric latitude at the surface but rather the angle formed by
Position P directly above the geocentric latitude.
Figure A is undoubtedly a Geodetic Latitude and Position P is above that
latitude.
Figure C places Position P directly overhead a position on the surface of the
earth to the south of the geocentric latitude shown.
Figure D is a colatitude.
Therefore, Figure B is correct.
However, we do feel that the legend in the diagram "gl
= geodetic latitude" is somewhat misleading as it doesn't apply to all
Figures.