Chapter 1 Surface Navigation Systems

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