BOAT NAVIGATION
`FOR THE REST OF US
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`

`

`

`To m~ father, Bill Sr., who taught me much about
`
`navigating through life, as well as his excellent
`
`methods of finding the way in the outdoors,
`qfl.oat, and on the road.
`
`International Marine
`AOirisiono(71mM<Gtmo-HillComptmia
`
`i'l
`
`-' l~ 13 1415 16 17 QVS 20 19 18 1716
`
`Copyright© 1995, 2001 In~eI1la1:1onal Marine
`All rtghts reserved. The publisher takes no responsibility for
`the use of any of the ma:tertals or methods described in this
`book, nor for t:lle products thereof. The name "International
`Marine• and the International Martne logo are trademarks of
`The McGraw-Hill Companies. Prtnted in the United States of
`Amert ca.
`Library of Congress Catal.oging-in-Publicatton Data
`Brogdon, Bill.
`Boat navigation for the rest of us : finding your way by
`eye and electroJJics / Bill Brodgon ; illustrated by Rob
`Groves.-2nd ed.
`p.
`cm.
`Includes index.
`ISBN 0-07-137226,1 (alk. paper)
`1. Navigation-United States. 2. E_lectronics in naviga(cid:173)
`tion-United States. 3. Pilots and pilotage-United States.
`J,Titje.
`VK555.B794 2001
`00-050592
`623.89-dc21
`Questions regarding the content of this book should be
`addressed to international Marine, P.O. Box 220, Camden,
`ME 04843; 'WWw.inteinatlonalma.rine.com
`Questions regarding the ordertng of this book should be
`addressed to The McGraw-Hill Companies, Customer Service
`Department, P.O. BQx 547, Blacklick, OH 43004
`Retail customers: 1-800-262-4729
`Bookstores: 1-800-122-4 726
`Photos by the author unless otherwise noted
`Printed on 60# Finch opaque
`Design by Patrtce M. Rossi
`Production and page layout by Janet Robbins. Second
`edition by Nancy Benner
`Edited by James R Babb, Don Casey, and Alex Barnett
`A special tl:lailks to Matt Dennon for the loan of.his boat,
`Bandit. used in the front cover photograph.
`
`4
`
`

`

`Contents
`
`List of Sidebars
`Acknowledgments
`x
`Introduction
`
`vii
`
`viii
`
`I. How We Navig•te
`Going to an Object in Sigllt
`2
`Course, Speed, and Time: The DR
`Finding the Boat's Position
`5
`Electronic Aid-to-Navigation Systems
`8
`Blending Visual, Instrument, and Electronic Information
`
`4
`
`9
`
`2. Charts and Publications
`Charts
`11
`Latitude and Longitude
`Chart Sea.le and Prqjection
`Chart Symbols
`18
`Direction and Distance
`Depths
`28
`Chart Dates and Corrections
`Great Lakes Charts
`32
`Charts for Rivers and Reservoirs
`Publications
`36
`
`12
`16
`
`23
`
`30
`
`35
`
`3. Navigation Instruments and Equipment
`'Ille Compass
`39
`Direction
`40
`Va.rtation and Deviation
`42
`Bad Compass, Good Course
`Depthfinders
`50
`Types of Depth.finders
`55
`Depth Corrections
`Choosing a Depth.finder
`
`51
`
`57
`
`49
`
`1
`
`11
`
`39
`
`5
`
`

`

`58
`
`Speed and Distance Logs
`Tune
`59
`Binoculars
`60
`A Navigator's Kit
`Radar
`65
`Radar Measurements: Range and Bearing
`
`61
`
`99
`
`4. Aid•to-Navigation Systems
`Visual Aids to Navigation
`69
`71
`Color, Shape, Lights, and Numbers
`Itttrcicoastal Waten.vay Aids to Navigation
`Sound Signals
`77
`The Global Positioning System and Loran-C
`Plotters
`82
`Additional Similarities and Differences · 84
`Accuracy 87
`Coverage
`92
`Choosing an Electronic Navigation System
`Choosing a Receiver
`95
`96
`Differential GPS and WAAS
`Radiobeacons and Radio Direction Finders
`Ra cons
`99
`Other Radionavigation Systems
`
`67
`
`76
`
`79
`
`93
`
`97
`
`69
`
`100
`
`S. Finding Where You Are
`100
`Seaman's Eye
`Radar and Seaman's Eye
`Taking Departure
`11 O
`Ded (Dead) Reckoniilg-The DR
`111
`Tune, Speed, and Distance Calculations
`Time
`113
`Speed
`113
`Distance
`115
`Doing the Calculations Mentally
`Direction and Tune
`117
`Unes of Posj~on and Fixes
`
`11 O
`
`117
`
`113
`
`'•.: _,_,
`
`115
`
`iv
`
`6
`
`

`

`119
`120
`
`123
`
`125 ·
`
`128
`
`Objects for Lines of Position
`Fixes from Lines of Position
`Radar Lines of Position
`121
`Line-of-Position and Fix Errors
`124
`Ranges
`Estimated Positions
`Distance Off
`126
`Electronic Navigation Systems
`Waypoints
`130
`Measuring and Storing Waypoints with a Receiver
`131
`131
`Plotting GPS and Loran-C Positions on a Chart
`Position with Respect to Waypoints
`134
`Using Waypoints Measured by Another Receiver
`135
`Converting Waypoints from Loran-C to GPS
`Corrections to Waypoint Positions
`136
`Avoiding GPS and Loran-C Errors
`137
`Check before Getting Underway
`137
`Electronic Position Jumps
`137
`Out of Tolerance Signals
`138
`
`135
`
`142
`144
`144
`
`e. Finding Where to Go
`Seam~·s Eye
`140
`Frozen Ranges
`Steering Clear
`Weiter Colors
`Waves
`145
`Going to Distant Destinations
`146
`148
`Electronic Navigation Systems
`Coping with Current
`153
`Plotting
`153
`Ca1culclting the Lead Angle
`SlwrtcutLeadAngles
`155
`Practical Metlwds
`156 , .
`Following the Desired Track Using a Navigation Receive:r:·
`157
`Bearing to Waypoint
`Cross-'ITack Error
`· 158
`
`155
`
`140
`
`157· :,
`
`y ,
`
`7
`
`

`

`159
`
`159
`Course Made Good
`Estimated Time En Route
`159
`SCratch Waypoints
`Staying in Good Water
`161
`Losing Electronic Navigation
`162
`Radar
`162
`Blending Electronic and Visual Navigation
`Island Chains, Marshes, and Resetvoirs
`River Navigation
`169
`Night Navtgation
`172
`Navigation in Fog
`175
`Radar for Collision Avoidance
`176
`Collision Avoidance in Poor VistbUity
`
`164
`166
`
`183
`
`187
`
`7. Special Techn_iques
`Riding a Line of Position
`The Deliberate Miss
`188
`The Electronic Navigation Hook
`Look Behind You
`191
`Things That Go Wrong
`192
`193
`Signs ofTrouble
`193
`Data erttry Errors
`Different Bearings to a Wqypoint
`194
`Shifting Waypoints
`Which One Is Wrong?
`194
`Onboard Interference
`195
`External 'nterjetence
`197
`Moving the Receiver Long Distances
`Cross-TrackErrorJumps to Zero
`
`190
`
`193
`
`197
`197
`
`187
`
`Appendix A. How OPS Works
`198
`Appendix B. How Loran-C Works
`202
`Appendix C. Good, Bad, and Ugly Receiver Features
`Glossary
`209
`Index
`212
`
`205
`
`I
`I
`
`l'
`a
`
`I
`~
`
`vi
`
`8
`
`

`

`Sidebars
`
`Chapter2
`A Better Way to Measure
`Signal Information
`20
`The Angles
`24
`30
`Protecting Charts
`Making a Custom Chart
`
`14
`
`32
`
`Chapterl
`48
`Adjusting a Compass
`Leadlines: Crude but Reliable
`Radar Adjustments
`66
`
`55
`
`Chapter4
`Western River and State Aids to Navigation
`GPS: Selective Availability EliJilinated
`89
`Accuracy Measures
`91
`Better Than Differential?
`
`98
`
`77
`
`Chapters
`119
`Parallel Unes
`The Easiest Way to Find Distance Off: Why It Works
`129
`Evaluating GPS and Loran-C Fixes
`Beginning with an Electronic Receiver
`130
`SaVing a Waypo1nt
`132
`
`128
`
`143
`
`184
`
`vii
`
`Chapter6
`Deep-Draft Channels·
`,' ·Rule of Sixty · 145
`. .
`161
`Finding the Lay Une
`·International and Inland Rules and Radat
`'
`
`'
`
`'
`
`9
`
`

`

`Acknowledgments
`
`It would be impossible to acknowledge all who COI)tributed to this book, by
`teaching, by example, by expertmenting, by inventing, by wrttlrlg about naviga(cid:173)
`tion. Tennyson (speakip.g of that great navigator, Ullyses) wrote, "I am part of all
`that I have met, yet all experience ls an arch wherethrough gleams that untrav(cid:173)
`elled world, whose margin fades for eV'er and for ever when I move . . . " Isaac
`Newton said, "I have stood on the shoulders of giants." I am especially conscious
`of the keen minds and courage of those who have built this art and science over
`the centUrtes. Newton, for example, invented logarithms and the slide rule in
`addition to discovering tlie laws of motion. Navigation was prtmttive prior to his
`discoveries.
`
`I now regard myself as quite fortunate to have attended an excellent public
`high school ftl an era before discipline and high academic denuµids began to slip.
`Mrs. Phyllis Peacock was most memorable, smoothing some of the rough edges
`from her students' grammar, de~ding that we wrtte well. yet always encotirag(cid:173)
`ing us. I served in the U.S. Coast Guard durtng a long career at sea and in the
`aids to navigation mission. Many officers continued to teach me, particularly Roy
`Hutchins, Captain of Chilula, my second ship. I was fortunate to have dozens of
`quartermasters and radarmen assigned to my ships, who were bright, profes(cid:173)
`sional, inventive, and eager to work out new ways of doing navigation tasks,
`Authors and cartographers of the past recorded excellent methods of piloting.
`Ship pilots unselfishly taught me valuable seerets of their profession.
`
`Despite these advantages, I did not start writing for publication until the Lord
`anS\Yered a prayer for help in financial assistance with our children's early edu(cid:173)
`cation. Wi@n days, Jim Martenhoff, then boating editor of the Miamt Herald.,
`called and asked me to Write an article for a tabloid boating magazine he edited.
`Jim got me started Writing about navigation and seamanship and taught me
`much about the art of Writing. I also owe m:uch to the many magazine editors who
`bought my work, encouraged me, and taught me more about Writing.
`
`As I wrote, I gained knowledge. A pilot from Alaska taught me a simple
`method of detecting an electronic navigation error. I was fortunate to be deputy
`chief of Coast Guard ~when we were studying l..Qran-C and GPS performance,
`differential systems, and electronic charts. The many authors of technical articles
`for the Institute of Navigation, the International Loran Association, and the
`Hydrographic Society have added greatly to my knowledge. Many manufacturers
`allowed me to use LOran-C and GPS receivers for tests, and I applied controlled
`ex:pertments and statistical methods I had studied in graduate school to evaluate
`their performance. Commercial fishermen such as Julius Collins and dive charter
`boat operators such as .Buzz Mitchell showed me practical methods of using loran
`for highest accuracy.
`
`10
`
`

`

`More immediately, Jim Babb of International Marine helped me develop the
`idea of this book from a quite different initial idea. Don Casey (author of This Old
`Boc:it) read the typescript, found many of the errors, and helped me make the text
`and sketches easier to under8t;and. Rob Groves took my raw sketches and turned
`them into drawings that depict the ideas beautifully. Pamela Benner took over the
`editorial work after Jim left International Marine and has been most thorough
`and patient. Even so, I would not have completed this book without the support
`and encouragement of my dear wife. Joyce, who read it frequently and helped me
`reVise obscure or dtfflcult-to-understand passages. Despite all this help, some
`errors may remain; they are my responsibility.
`
`The Second Edition
`In the short space of six years, radionaVigation systems have changed so
`rapidly that it has become necessazy to publish a second edition to reflect the
`changes. Several manufacturers have allowed me to test their equipment or pro(cid:173)
`grams to ensure that the information is as up to date as possible. Alex Barnett
`and D; A. Oliver a:t International Marine have been a big help in complet:f,ng this
`edition.
`
`The Global Positioning System (GPS) has become extremely popular due to
`the decreased cost a,nd improved capability of receivers. In addition, the
`Department of Defense (DOD) improved GPS accuracy dramaUcally ori 1 l\fay
`2000 by eliminating the deliberate accuracy reduction, Selective Availability (SA).
`This welcome change gtves civilian navigators accuracy that is about five times as
`good as it was prior to the change.
`
`Improving GPS accuracy inE!.de all of the references to it in the first edition
`incorrect. 'I'hj.s second edition includes the best available estimates of GPS accu(cid:173)
`racy, obtained by collecting and analyzing data. As of December 2000 DOD has
`not released the new GPS performance speciftcation, but the estimates should be
`close.
`
`Several older electronic aids-to-navigation-systems have been eliminated:
`Omega, SATNAV, and Decca. The Coast Guard has completed the coastal
`Differential GPS system using radiobeacons. The FM has started broadcasting
`Differential GPS corrections by satellites as they develop the Wide Area
`Augmentation System (WAAS) for GPS. The Raytheon Corporation began selling
`WAAS-augmented marine GPS receivers in the summer of 2000. Seve:i:'al manu(cid:173)
`facturers of GPS receivers now include advanced plotters, and electronic chart
`packages are beginning to become popular on laj-ger yaGhts. l..oran'-C, once the
`most popular system, remains in use aboard a large iiilID.ber of boats as the
`Coast Guatd improves the transniitter system to provide an independent yet com-
`plementary system to GPS for navigation and timing.·
`·
`·
`:··'
`
`~ ' :
`
`.
`
`. ~ ·-;'
`
`11
`
`

`

`Introduction
`
`Many people buying a first boat almost immediately discover their need to
`navigate. They're smart, successful in demanding occupations, and more than
`capable of understanding navigation-they just don't kr)ow much about it.
`They aren't alone. Many boats carry sophisticated navigation equipment thf!ir
`skippers hlive barely begun to learn to use. Confusing operator's manuals are
`intimidating. Maybe the skipper's 1.J.Ilderstanding of charts or compasses is limi.:ed.
`Some may have taken a basic navigation course only to find classroom methods
`difficult to use aboard a small boat. The pedantic explanations of obscure phe(cid:173)
`nomena too often featured in courses and texts can also discourage a skipper
`wanting simple directions for finding his way around.
`A number of boatowners have learned to use a Global Positioning System
`(GPS) receiver or Loran-C competently but depend on it totally. When they ven(cid:173)
`ture offshore, everything is fine as long as the receiver is working; but vrhen
`something does go wrong, their single source of information vanishes. Although
`the boat has the equipment to navigate without GPS or Loran-C, these skippers
`are unprepared to use it. They ate lost.
`Others have simply put off installmg a key navtgation instrument because
`they don't know what it will do for them. After all, they go out and get back home,
`don't tbey? Yes, but the trips might be more enjoyable were there less worry
`about getting lost and less time spent recovering from poor navigation.
`Struggling with navigation, getting lost. or going aground seriously detracts
`from the fun of owning a boat. These problems may lead some boatowners to
`avoid using their boats as much as they would like to. This book is meant to help
`all navigators steer around the shoals and eddies of inappropriate methods and
`learn to navigate easily, accurately, and without fuss. Even those of you who are
`already competent will find new ideas for using your navigation skills or doh:lg
`some things more easily. After all, navigation should be an adjunct to boating,
`not a full"time job.
`When I first went out on boats, I learned to find my way around by seaman's
`eye-tl:ie relationship of the size and shape of visible objects and the angles
`between them, supplemented by the color of the water and the appearance of the
`waves. As my experience e>n the water progressed, skippers on larger boats taught
`me about compass courses and the relationship between speed and distance.
`In 1948 I bought a copy of PUoting, Seamanship, and Small Boat Handling by
`C. F. Chapman and began to unfold the mysteries of chart and compass. In those
`days Chapman's was organized into a series of lessons, and I .studied them
`intently. In 1952 I received an appointment to the U.S. Coast Guard Academy,
`where I learned much more about piloting, charts, celestial navigation, radar, and
`loran through formal courses and practical experience. When I graduated, I
`became navigator of a cutter and began to learn in earnest. I blush to think how
`immature my knowledge was then, but I served under some demanding skippers
`who eX:pected me to learn .more and more.
`During my shipboard assignments, I served as navigator, operations officer,
`executive officer, and as commandiriQ: officer of three ships, with i!I'<>Wiru! resoon-
`
`12
`
`

`

`INTRODUCTION ·.
`
`xi
`
`sibility for safe navigation. I taught. navigation: chartwork, piloting, how to use
`radar and loran, and how to take, reduce, and plot celestial lines of position. I
`studied in. detail many of the things I had taken for granted about the art and sci(cid:173)
`ence of navigation. I worked in the Coast Guard's Aj.ds-to-Navigation n.nssion,
`including operating, teaching, and managing the program. I was involved with
`new developments in research, and in evaluating the capabilities of optical,
`sound, and electronic navigation systems.
`While I served in ships, I was never far away from boats, and I struggled to
`adapt my knowledge of ship navigation to boats. I fished for sport. I made trips on
`commercial fishing boats. I navigated in some long ocean sailing races. I began to
`feel that, except for the vital invention of the depthftnder, coastwtse boat naviga(cid:173)
`tion remained in the nineteenth centwy. Boat compasses were seldom adjusted
`correctly, and it was dtftlcult to take bearings with them. It was even more dtftl~
`cwt to plot courses or be~gs or tomeaatire distances. Very feW boats had loran
`or radar. Yet all of these techniques and equipment were fundamental to ship
`navigation, to my profession.
`I began to mimic techniques I found in old sailing directions, ratters (route
`description books}, and charts, methods of earlier navigators that were still up to
`date aboard. boats. I learned other techniques from commercial fish~en. ship
`pilots, and charter~boat skippers.
`Then the revolution started.
`Loran-A came into common use aboard commercial fishing boats in the
`1960s. In the 1970s fishing skippers began perfecting methods of navigating by
`Loran-C that were superior to those I had learned. The next generation of
`receivers could calculate the direction and distance to stored waypoints. By the
`1980s, Loran-C receivers were so advanced and so tnexpenstve that most boats
`operating offshore began carrying them. I put a '"water-resistant" one on a 20-foot
`open outboard and put it to a real test. What a revelation!
`I had navigated ships by loran, satellite, radar, and gyrocompass, piloted
`commercial fishing boats with Loran-C and radar, and was at home finding my
`way around in small boats with a compass and a depthfinder, but to carry a pre(cid:173)
`cision navigation receiver in an open boat-that was something. Supplementing
`traditional small-boat navigation with modern electronics overcomes many of the
`problems of boat navigation that stem from limited space, small crews, and the
`need to do many things in addition to navigation.
`By 1993, when GPS beca.ID.e available full-time. quality receivers had become
`readily available and prices were declining steadily. Despite the increasing avail(cid:173)
`ability of sophisticated navigation equipment for small boats, texts and courses
`have remained weak in teaching small-boat navigation skills. Students learning
`chartwork on the kitchen table find this new skill out of place aboard a small.
`wet, lively boat. Books on electronic navigation ignore visual navigation. Books on
`visual navigation ignore electronics-and fog. Cla.ssic texts like Dt1.ttpn and
`BoWditch are eX:cellent for ship navtgation but less practical for boats.
`Navigation books tend to concentrate on open waters where you can steer
`straight cc;>urses to the n~ destination, but what about people who use boats in
`rtvers, reservofrS, and marshes? They can use modem navigation equipment, too,
`although there has been precious little written about how to do it.
`One good guidebook dismisses the need for Loran-C in inland waters, yet
`makes frequent references to things difficult to find without electrontcs....(cid:173)
`unmarked creek entrances, aids to navigation long distances apart, poorly
`
`13
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`

`

`xii
`
`BOAT NAVIGATION FOR THE REST OF US
`
`marked routes. Most. books ignore the Vital subject of using radar for collisic:m
`avoidance.
`Many people have ask~d me to combine the seven years of 11avigation
`columns I wrote for Motor Boating & Saatng into a book, but those were hints and
`ideas for experienced navigators. Instead, I've written a book for new navigators
`as well, one that provides siinple rules of. thumb along with the more COlllpleX
`methods of solving problems.
`This is a book about the practical way to find your way around in a boat-not
`chart-table, gyro-repeater, radar-assisted ship navigation and neither wholly
`visual nor wholly electronic, but a practical blend of techniques designed to make
`it easy to ful.d your way around, even aboard a small open boat.
`A new navigator can learn the basics first and come back later to learn about
`more complex methods. The book is orgaruzed to allow the experienced skipper to
`skim familiar areas and concentrate on new material. Parts of this book are a
`smorgasbord of information that will become more interesting with increasing
`experience. Many problems are discussed that affect electronic navigation, some
`that will become of interest only as navigation skill advances. Little is lost if read(cid:173)
`ers skip sections about equipment they don't use.
`This book combines visual and electronic navigation, chartwork, and trip
`pla.nnip.g for boats-power or sail-taking into consideration the limitatioi::ts of
`space and time. It includes information about navigating rivers and large reser(cid:173)
`voirs. It is specifically gea,red to North America. (A reader in east longitude or
`south latitude will have to make adjustments due to location.) It doesn't include
`information about compass theory, or about celestial navigation. Instead it con(cid:173)
`centrates on practical ways to make boat navigation easy, a.nd it provides more
`information about the use of electronic equipment than just a list of features. It
`is, in short, an attempt to provtde you with a no-fuss method of navigating your
`boat. If it does that, it will have fultllled its purpose.
`Your book will be most useful if you mark it to fit your needs as you read it.
`Mark iinportant sections, underline or highlight key words, and make notes in
`the margins. You will be able to remember new or important facts better, and it
`will be easier to find them later. These are key steps in learning.
`
`14
`
`

`

`CHAPTER I
`
`How We Navigate
`
`N.vtgation is the art and science of finding where we are and of finding
`otit way safely to our destination. We usually start at a known position, such as
`the seaward end of a channel, and go to another position a number of miles
`away-a buoy, a place where we change course, or a fishing spot. Our funda(cid:173)
`mental questions are: Wha.t is the direction to our destination? When will we
`arrive? Are there any hazards along the way? After we have traveled for a while,
`another question may arise: Where are we now? Let's preview the ways we
`ariswer these questions.
`We m.ake four essential measurements in navigation: depth, speed,
`direction, and time. Navigators have long relieq on "lead, log, and compass" but
`had rather crude timepieces until about a century
`ago. Today we are blessed with excellent instruments
`for these four measurements. Along with a chart, the
`navigator's basic tools are a depth.finder, a speed or
`distance log, a compass, and a watch. We make
`other measurements: radar measures the distance
`and direction to an object such as a point of land.
`~lectronic aid-to-navigation system receivers make
`time measurements of precise radionavlgation sig(cid:173)
`nals, and calculate the boat's position.
`We use charts to identify aids to navigation and
`landmarks, to avoid shoals and other hazards, and to find or show the boat's
`position. Using a chart, we ca.n find the direction and distance from the bm:i.t's
`position to a destination. We can see the depths along the way. It can help us
`determine where we are long after leaving the last known position. A chart is like
`a road map, but With a grtdwork of latitude and longitude lines instead of crosi;;
`streets. A navigator needs to know how to measure distances and to plot posi•
`tions and courses on a chart, but this book includes methods that can substitute
`for some of t:he chartwork.
`We start by finding wl:iete we are. Then we find the direction and distance from
`there to a destination, using either a chart or a navigation receiver. We steer tl:ie
`course to a distant destination by compass. We divide the distance by the boat;s
`speed to determine the number of hours en route. None of this is complex, but peo-
`
`Our fundamental questions
`are: What is the directidn to
`.our destination? When will
`we arrive? Are there any
`hazards along the way?
`
`15
`
`

`

`

`

`

`

`

`

`

`

`

`

`

`

`

`

`HOY'/ WE NAVIGATE -
`
`9
`
`LOPs; the receiver uses electrortic,LOPs to calculate the position, Second, it cal(cid:173)
`culates the direction and distance to the waypoint at our destination. It saves us
`the effort of plo~g the position, .drawing a line to the destination, and measur(cid:173)
`ing its direction and length. -The receiver also gives us a way of checking our DR
`navigation. Is it any wonder that these electronic aids to x:ia,vigat,ion are popular?
`Navigation receivers are particularly valuable when we've been sailing .or
`fishing for several hours and don't know where we are with any degree of accu(cid:173)
`racy. Without GPS or another navigation system receiver, we head in the. gen(cid:173)
`eral direction of a landlilark. When we see it, we can determine a .rough posi(cid:173)
`tion. Often we wind up off to one Side or the other and have to change course to
`go to our destination. With a navigation receiver, we simply enter t11e desired
`waypoint as the destination, and in a few seconds the display shows the direc(cid:173)
`tion and distance to the waypotnt from our current position.
`Although today's electronic navigation systems lift boat navigation to a high
`level, they are not easy to lean;i. to use. It is particularly trying when you can't
`stop the recetvet from beeping at you mstead of answering tbe keys, and the
`instruction manual jumps between normal and rare operations. Tllis book intro(cid:173)
`duces the more important features of electronic navigation systems first, saving
`the others for later sections.
`
`Blending Visual, Instrument, and Electronic Information
`A boatowner who learns the fundamentals of navigation can eajoy his boat
`free of much of the wony that accompanies uncertain positions. At first, navigation
`requires a lot of mental effort, but it soon becomes
`routine and easy. Every navigator started with a low
`level of knowledge. Skill in navigation isn't inherited
`or bought, it is learned. This book is a plan for learn(cid:173)
`irlg, beginning with the things that are most useful.
`A skipper should match the navigation method to
`the trip. Suppose you are heading along a rel_atively
`straight coast from one harbor entrance to the next.
`You could just keep the coast to starboard and find
`the next entrance, but if you find the course to steer,
`you won't zigzag as much as when steering by watch(cid:173)
`ing the coast. Enter a destination waypoint for the
`second harbor into your navigation receiver, and it
`will provide continuous direction and distance to ilie
`entrance. If you divide the distance by the boat speed, you can detennirle wben
`you will arrive. Compare the depth with the chart, and you get a useful line of
`posi:tion. Note the time when you depart the first harbor, and you can keep up
`With the distance yotJ. have traveled. Your thought process might be: "It's been a
`half hour since we left, and the boat makes 20 knots, so we're about 10 ~~
`down the coast and on the 30-foot contour."
`A navigator does several of these simple things, depending on the distance,
`the visibility, and hazards along the route. As new conditicms increase the danger
`or uncertainty, the navigator responds by setting intermediate waypoints, steer(cid:173)
`ing carefully, timing legs of the trip, finding the effect of current, and using other
`features of a navtgation receiver.
`
`As new conditions increase
`the danger or uncertainty, the
`navigator responds by setting
`intermediate waypoints,
`steering carefe.lly, timing legs
`of the trip, finding the effect of
`cr.1.Trent, cind using other fea(cid:173)
`tures of a navigation receiver.
`
`23
`
`

`

`10 .
`
`BOAT NAVIGATION FOR THE REST OF US
`
`GPS and Loran-G receivers ate useful even on short, clear-weather tlips. You
`may be a beginner, but with a navigation receiver you can navigate better than
`the expert who doesn't have one aboard. A navigation receiver performs many of
`the functions that previousiy required plottiIJ,g on a chart, but it isn't perfect: It
`shows the direct course to a waypoint, ignoring intervening rocks, shoals,
`islands, even continents. The navigator has to use a chart to make sure the way
`is clear.
`·A receiver also can show the effect of current, the enemy of accurate DR navi(cid:173)
`gation. However, these receivers are so good that it is easy to depend on them too
`much. A receiver sometimes gives wrong information, whether from misentered
`waypoints or from signal or internal problems. Can you detect these errors?
`Wh¢Ii a receiver fails, a beginner's mind can be as blank as the dead screen. If
`you learn workable boat navigation methods while you use an electronic naviga(cid:173)
`tion system receiver, this won't happen to you. With this book, you'll learn how to
`blend electronic navigation with visual navigation, charts, and instruments.
`When a receiver gives false information, you11 be able to detect the problem.
`WJ:J.en it gives no information at all, you wiil still know where to go-just like the
`expert.
`
`24
`
`

`

`CHAPTER 2
`
`Charts and Publications
`
`charts are essential to navigation. You identify landmarks, find depths,
`measure distances and directions, and find your way to a destination using
`a chart. To find the boat's position, you compare the depth, distance, and direction
`measured by instruments aboard the boat wttJ.:>,. the depth; distance, and direc(cid:173)
`tiOI1 sh()\VIl on a chart. You write the time on the chart when the boat is at a known
`position, and you use positions from electronic navigation receivers with a chart.
`The information in this chapter is elementary, but understanding