Basic Flight Navigator : The Earth

Shape and also Size
For the majority of navigational purposes, the world can be assumed to
be a perfect sphere, even though in reality it's certainly not. Inspection
of the world s crust reveals there can be a height variation of
approximately 12 miles within the top associated with the tallest mountain
with the particular bottom associated with the deepest point in the ocean. A more
noticeable deviation from round typically is brought about by a mixture of
the actual earth s rotation and also its structural flexibility. Whenever taking
the particular ellipsoidal shape associated with the planet into account, mountains
appear very insignificant. The peaks associated with the Andes usually are much
farther within the center associated with the earth compared to Mount Everest.
Measured at the equator, the actual world can be around 6,378,137
meters in diameter, while the polar diameter is approximately
6,356,752.3142 meters. The particular difference with regard to many of these diameters
typically is 21,384.6858 meters, and this particular difference may be employed to
express the ellipticity of the world. The ratio between this particular
difference plus the equatorial diameter is:
Ellipticity = 21,384.6858 = 1
6 378,137 298.257223
Since the actual equatorial diameter exceeds the polar diameter by
only 1 part throughout 298, the world is actually almost spherical. A symmetrical
human body having the particular exact same dimensions because the world, however alongside
a smooth surface, is known as a great ellipsoid. The actual ellipsoid can be
at times described as a spheroid, or perhaps a particular oblate spheroid.
In Figure 1-1, polar north (Pn), east (E), polar south (Ps),
not to mention west (W) represent the actual surface associated with the earth. Pn and in addition Ps
represent the actual axis of rotation. The particular world rotates from west to
east. Almost all points within the hemisphere Pn, W, Ps approach the
reader, whilst those within the opposite hemisphere recede from
the actual reader. The actual circumference W-E typically is called the equator,
that is defined as that imaginary circle found on the surface of
the particular earth whose plane passes through the actual center of the earth
as well as is actually perpendicular to be able to the axis of rotation.
Great Circles and even Small Circles
A superb circle can be defined as a circle on the surface of the sphere
whose center and also radius happen to be those associated with the sphere itself. It is actually
the actual biggest circle that may be drawn found on the sphere; it's the particular
intersection with all the surface of the earth of any plane passing
through the world s center. The particular arc of the awesome circle typically is the actual
shortest distance between two points about a sphere, just because a
straight line can be the particular shortest distance between couple points on a
airplane. About any sphere, an indefinitely large amount of great