Navigation is both an art and a science. The
science part is the development of instruments and
procedures of navigation, along with the
computations involved. The art is the skillful use of
the instruments and the interpretation of the data.
This combination has led some to call navigation a
“scientific art.”
The beginning navigators practiced the science of
navigation, in that they gathered data and used it to
solve a navigational problem in a mechanical way. It
takes many hours of flying for navigators to realize
that their total role involves not only the mechanics of
navigation, but an integration based on judgement.
They build accuracy and reliability into their
performance by applying sound judgment based on
experience. Navy navigators must be able to plan
missions covering every possible situation. In flight,
they must evaluate the progress of the aircraft and
plan for the remainder of the mission. High-speed
navigation demands that they have the ability to
anticipate changes in flight conditions and make the
correct decisions immediately ahead of those
changes.
The purpose of air navigation is to determine the
direction of travel needed to end up at the desired
location, to locate positions, and to measure distance
and time as a means to that end. This chapter deals
with the various types of navigation and the
equipment used in aviation navigation.
You must
know and understand this information in order to train
your subordinates.
METHODS OF NAVIGATION
Learning Objective: Recognize the various
methods of navigation.
There are certain terms that you must know to
understand navigation.
The navigator uses these
terms to express and accomplish the practical aspects
of air navigation. These terms are position, direction,
distance, and time. These terms are defined as
follows:
Position is a point defined by stated or implied
coordinates. It always refers to some place that can
be identified. A navigator must know the aircraft’s
immediate position before he/she can direct it to
another position.
Direction is the position of one point in space
relative to another without reference to the distance
between them. Direction is not in itself an angle, but
it is measured in terms of its angular distance from a
reference direction.
Distance is the spatial separation between two
points and is measured by the length of a line
joining them. On a plane surface, this is a simple
problem. However, consider distance on a sphere,
where the separation between points may be
expressed as a variety of curves. The navigator
must decide how the distance is to be measured.
This distance can be expressed in various units;
miles, yards, etc.
Time is defined in many ways, but for our
purposes, it is either the hour of the day or an elapsed
interval.
These terms represent definite quantities or
conditions that can be measured in several
different ways. The position of an aircraft may
be expressed as coordinates such as latitude and
longitude, or as being 10 miles south of a certain
landmark. It is vital that navigators learn how to
measure quantities and how to apply the units by
which they are expressed.
EARTH’S SIZE AND SHAPE
For navigational purposes, the earth is assumed to
be a perfect sphere, although it is not. There is an
approximate 12-mile difference between the highest
point and the lowest point of the earth’s crust. The
variations in the surface (valleys, mountains, oceans,
etc.) give the earth an irregular appearance.
Measured at the equator, the earth is
approximately 6,887.91 nautical miles in diameter.
The polar diameter is approximately 6,864.57 nautical
miles. This difference of 23.34 nautical miles is used
to express the ellipticity of the earth.
Great Circles and Small Circles
A great circle is defined as a circle on the surface
of a sphere whose center and radius are those of the
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