CHAPTER 1
SURFACE NAVIGATION SYSTEMS
INTRODUCTION
Today’s Navy uses various navigational systems
in the fleet. As an ET, you will be responsible for
maintaining these systems.
In this volume, we will cover navigation
fundamentals, the Ship’s Inertial Navigation System,
Navy Satellite Navigation System, NAVSTAR Global
Positioning System, fathometers, and TACAN. Let’s
start with navigation fundamentals.
NAVIGATION FUNDAMENTALS
In simple terms, navigation is a method of getting
from one known point to some distant point. Piloting,
celestial navigation, and radio navigation are the
commonly used methods. In this chapter, we will
discuss radio navigation and its components: dead
reckoning,
electronic
navigation,
and tactical
navigation. The tactical use of NTDS data (tactical
navigation)
was
covered
in
v o l u m e 3 ,
Communications Systems. However, we will review
it briefly here to help you see how it fits into radio
navigation. We will then discuss dead reckoning and
electronic navigation in more detail.
TACTICAL NAVIGATION
You must understand the difference between
navigation in the traditional sense and tactical
navigation. Traditional navigation and piloting are
concerned primarily with safe maneuvering of the
ship with respect to hazards such as shoals, reefs, and
so forth. Tactical navigation is not directly concerned
wit h maneuvering the ship in navigable waters. For
the purposes of tactical navigation, absolute position
is unimportant except to the extent that it supports
determining the relative position of hostile targets and
friendly cooperating platforms.
Remember, tactical navigation deals primarily
with fixing the location of the platform to (1) enable
installed weapon systems to function against intended
targets, (2) prevent ownship loss to or interference
with friendly weapon systems, and (3) coordinate
ownship weapons systems with those of other
platforms to achieve maximum effect.
In tactical navigation, navigation data is used by
combat systems, including NTDS, to ensure accuracy
in target tracking.
Ship’s movements are
automatically recorded by computer programs for
applications such as gun laying calculations and Link
11 position reporting. Ship’s attitudes (pitch, roll, and
heading) are transmitted to various display and user
points, and electronic or mathematical computer
stabilization is accomplished, depending on the
system. For example, pitch and roll are used by
NTDS, missile, sonar, gun, and TACAN systems for
stabilization data and reference. Heading is used by
the EW direction finding, sonar, and radar systems for
true and relative bearing display. Ship’s navigation
and attitude data are provided by various equipment,
depending on ship class.
DEAD RECKONING
Dead reckoning is the estimating of the ship’s
position between known navigational points or fixes.
Radio navigation, consisting of terrestrial systems
such as OMEGA and LORAN, and space-based
systems, such as SATNAV, TRANSIT, and
NAVSTAR GPS, provides accurate positions at
specific fixes. However, with the exception of some
gunfire support systems that provide nearly constant
positional updates with respect to a fixed beacon or
prominent landmark, there is a limit to how often
fixes can be obtained. This requires us to dead reckon
(DR) between the fixes. Dead reckoning can be as
basic as a DR line for course and speed on a plotting
sheet or as sophisticated as an estimate made by an
l-l
