Pub. No. 9
`
`THE
`AMERICAN
`PRACTICAL NAVIGATOR
`
`AN EPITOME OF NAVIGATION
`
`ORIGINALLY BY
`
`NATHANIEL BOWDITCH, LL.D.
`
`2002 BICENTENNIAL EDITION
`
`Prepared and published by 1he
`NATIONAL IMAGERY AND MAPPTNG AGENCY
`Bethesda, Maryland
`
`<O COPYRIGHT 2002 BY THE NA TJONAL fMAGERY AND MAPPING AGENCY, U.S. GOVERNMENT.
`NO DOMESTIC COPYRIGHT CLAIMED UNDER TITLE I 7 U.S.C. ALL RIGHTS RESERVED.
`
`111~1111D1~11111mlf]l~m11~11u~~1mrn11
`NSN 7642014014652
`NIMAREF NO NVPUB9V1
`
`For sale by the Superinteodant ofDocuments, U.S. Govemment Printing Office
`Internet: book.store.gpo.gov Phone: toll free (866) 512-1800; DC area (202) 5 12-1800
`Fax: (202) 512-2250 Mail Stop: SSOP, Washington, DC 20402-0001
`
`1
`
`Navico Ex. 1018
`
`

`

`Last painting by Gilbert Stuart ( 1828). Considered by the family of Bowditch to be the best of
`various paintings made, although it was unfinished when the artist died.
`
`2
`
`

`

`NATHANIEL BOWDITCH
`(1773-1838)
`
`Nathaniel Bowditch was born on March 26, 1773, in
`Salem, Mass., fourth of the seven children of shipmaster
`Habakkuk Bowditch and his wife, Mary.
`Since the migration of William Bowditch from
`England to the Colonies in the 17th century, the family had
`resided at Salem. Most of its sons, like those of other
`families in this New England seaport, had gone to sea, and
`many of them became shipmasters. Nathaniel Bowditch
`himself sailed as master on his last voyage, and two of his
`brothers met untimely deaths while pursuing careers at sea.
`Nathaniel Bowditch's father is said to have lost two
`ships at sea, and by late Revolutionary days he returned to
`the trade of cooper, which he had learned in his youth. This
`provided insufficient income to properly supply the needs
`of his growing family, who were often hungry and cold. For
`many years the nearly destitute family received an annual
`grant of I 5 to 20 dollars from the Salem Marine Society. By
`the time Nathaniel had reached the age of 10, the family's
`pove1ty forced him to leave school and join his father in the
`cooper's trade to help suppo11 the fami ly.
`Nathaniel was unsuccessful as a cooper, and when he
`was about 12 years of age, he entered the first of two ship(cid:173)
`chandlery firms by which he was employed. It was during
`the nearly 10 years he was so employed that his great mind
`first attracted public attention. From the time he began
`school Bowditch had an all-consuming interest in learning,
`particularly mathematics. By his middle teens he was recog(cid:173)
`nized in Salem as an authority on that subject. Salem being
`primarily a shipping town, most of the inhabitants sooner or
`later found their way to the ship chandler, and news of the
`brilliant young clerk spread until eventually it came to the
`attention of the learned men of his day. Impressed by his de(cid:173)
`sire to educate himself, they supplied him with books that he
`might learn of the discoveries of other men. Since many of
`the best books were written by Europeans, Bowditch first
`taught himself their languages. French, Spanish, Latin,
`Greek and German were among the two dozen or more lan(cid:173)
`guages and dialects he studied during his life. At the age of
`16 he began the study of Newton's Principia, translating
`parts ofit from the Latin. He even found an e1Tor in that clas(cid:173)
`sic text, and though lacking the confidence to announce it at
`the time, he later published his findings and had them ac(cid:173)
`cepted by the scientific community.
`During the Revolutionary War a privateer out of Beverly,
`a neighboring town to Salem, had taken as one of its prizes an
`English vessel which was carrying the philosophical library of
`a famed Irish scholar, Dr. Richard Kirwan. The books were
`brought to the Colonies and there bought by a group of
`educated Salem men who used them
`to found
`the
`
`Philosophical Library Company, reputed to have been the best
`library north of Philadelphia at the time. In 1791, when
`Bowditch was 18, two Harvard-educated ministers, Rev. John
`Prince and Rev. William Bentley, persuaded the Company to
`allow Bowditch the use ofits library. Encouraged by these two
`men and a third, Nathan Read, an apothecary and also a
`Harvard man, Bowditch studied the works of the great men
`who had preceded him, especially the mathematicians and the
`astronomers. By the time he became of age, this knowledge,
`acquired when not working long how'S at the chandlery, had
`made young Nathaniel the outstanding mathematician in the
`Commonwealth, and perhaps in the country.
`In the seafaring town of Salem, Bowditch was drawn
`to navigation early, learning the subject at the age of 13
`from an old British sailor. /\.year later he began studying
`surveying, and in 1794 he assisted in a survey of the town.
`At I 5 he devised an almanac reputed lo have been of great
`accuracy. His other youthful accomplishments included the
`construction of a crude barometer and a sundial.
`When Bowditch went to sea at the age of 21, it was as
`captain's writer and nominal second mate, the officer's berth
`being offered him because of his reputation as a scholar. Under
`Captain Henry Prince, the ship Hemy sailed from Salem in the
`winter of 1795 on what was to be a year-long voyage to the lie
`de Bourbon (now called Reunion) in the Indian Ocean.
`Bowditch began his seagoing career when accurate time
`was not available to the average naval or merchant ship. A
`reliable marine chronometer had been invented some 60
`years before, but the prohibitive cost, plus the long voyages
`without opportunity to check the error of the timepiece, made
`the large investment an impractical one. A system of
`determining longitude by "lunar distance," a method which
`did not require an accurate timepiece, was known, but this
`product of the minds of mathematicians and astronomers was
`so involved as to be beyond the capabilities of the
`uneducated seamen of that day. Consequently, ships were
`navigated by a combination of dead reckoning and parallel
`sailing (a system of sailing north or south to the latitude of the
`destination and then east or west to the destination). The
`navigational routine of the time was "lead, log, and lookout."
`To Bowditch, the mathematical genius, computation of
`lunar distances was no mystery, of cou1'Se, but he
`recognized the need for an easier method of working them
`in order to navigate ships more safely and efficiently.
`Through analysis and observation, he derived a new and
`simplified formula during his first trip.
`John Hamilton Moore's The Practical Navigator was
`the leading navigational text when Bowditch first went to
`sea, and had been for many years. Early in his first voyage,
`
`iii
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`however, the captain's writer-second mate began turning
`up errors in Moore's book, and before long he found it
`necessary to recompute some of the tables he most often
`used in working his sights. Bowditch recorded the errors he
`found, and by the end of his second voyage, made in the
`higher capacity of supercargo, the news of his findings in
`The New Practical Navigator had reached Edmund Blunt,
`a printer at Newbu1yport, Mass. At Blunt's request,
`Bowditch agreed to participate with other learned men in
`the preparation of an American edition of the thirteenth
`(1798) edition of Moore's work. The first American edition
`was published at Newburyport by Blunt in 1799. This
`edition corrected many of the errors that Moore had
`included.
`Although most of the errors were of little significance
`to practical navigation because they were errors in the fifth
`and sixth places of logarithm tables, some errors were
`significant.The most significant mistake was listing the
`year 1800 as a leap year in the table of the sun's declination.
`The consequence was that Moore gave the declination for
`March I, 1800, as 7°1 I'. Since the actual value was 7° 33',
`the calculation of a meridian altitude would be in error by
`22 minutes of latitude, or 22 nautical miles.
`Bowditch's principal contribution to the first American
`edition was his chapter "The Method of Finding the
`Longitude at Sea," which discussed his new method for
`computing lunar distances. Following publication of the first
`American edition, Blunt obtained Bowditch's services in
`checking the American and English editions for fu11her
`e1TOrs. Blunt then published a second American edition of
`Moore's thi1teenth edition in 1800. When preparing a third
`American edition for the press, Blunt decided that Bowditch
`had revised Moore's work to such an extent that Bowditch
`should be named as author. The title was changed to The
`New American Practical Navigator and the book was
`published in 1802 as a first edition. Bowditch vowed while
`writing this edition to "put down in the book nothing I can't
`leach the crew," and it is said that eve1y member of his crew
`including the cook could take a lunar observation and plot
`the ship's position.
`Bowditch made a total of five trips to sea, over a period
`of about nine years, his last as master and part owner of the
`three-masted Putnam. Homeward bound from a 13-month
`voyage to Sumatra and the Ile de France (now called
`Mauritius) the Putnam approached Salem harbor on
`December 25, 1803, during a thick fog without having had
`a celestial observation since noon on the 24th. Relying
`upon his dead reckoning, Bowditch conned his wooden(cid:173)
`hulled ship to the entrance of the rocky harbor, where he
`had the good fortune to get a momentary glimpse of Eastern
`Point, Cape Ann, enough to confirm nis position. The
`Putnam proceeded in, past such hazards as "Bowditch's
`Ledge" (named after a great-grandfather who had wrecked
`his ship on the rock more than a century before) and
`anchored safely at 1900 that evening. Word of the daring
`
`feat, performed when other masters were hove-to outside
`the harbor, spread along the coast and added greatly to
`Bowditch's reputation. He was, indeed, the "practical
`navigator."
`His standing as a mathematician and successful
`shipmaster earned him a well-paid position ashore within a
`matter of weeks after his last voyage. He was installed as
`president of a Salem fire and marine insurance company at
`the age of 30, and during the 20 years he held that position
`the company prospered. In 1823 he left Salem to take a
`similar position with a Boston insurance firm, serving that
`company with equal success until his death.
`From the time he finished the "Navigator" until 1814,
`Bowditch's mathematical and scientific pursuits consisted of
`studies and papers on the orbits of comets, applications of
`Napier's rules, magnetic variation, eclipses, calculations on
`tides, and the charting of Salem harbor. In that year, however, he
`turned to what he considered the greatest work of his life, the
`translation into English of Mecanique Celeste, by Pien-e
`Laplace. Mecanique Celeste was a summaiy of all the then
`known facts about the workings of the heavens. Bowditch
`translated four of the five volumes before his death, and
`published them at his own expense. He gave many formula
`derivations which Laplace had not shown, and also included
`further discoveties following the time of publication. His work
`made this infommtion available to American astronomers and
`enabled them to pursue their studies on the basis of that which
`was already known. Continuing his style of writing for the
`learner, Bowditch presented his English version of Mecanique
`Celeste in such a manner that the student of mathematics could
`easily trace the steps involved in reaching the most complicated
`conclusions.
`Shortly after the publication of The New American
`Practical Navigator, Harvard College honored its author
`with the presentation of the honora1y degree of Master of
`Ar1s, and in 1816 the college made him an honorary Doctor
`of Laws. From the time the Harvard graduates of Salem first
`assisted him in his studies, Bowditch had a great interest in
`that college, and in 1810 he was elected one of its Overseers,
`a position he held until I 826, when he was elected to the
`Corporation. During 1826-27 he was the leader of a small
`group of men who saved the school from financial disaster by
`forcing necessary economies on the college's reluctant
`president. At one time Bowditch was offered a Professorship
`in Mathematics at Harvard but this, as well as similar offers
`from West Point and the University of Virginia, he declined.
`In all his life he was never known to have made a public
`speech or to have addressed any large group of people.
`Many other honors came to Bowditch in recognition of
`astronomical,
`mathematical,
`and
`marine
`his
`accomplishments. He became a member of the American
`Academy of A1ts and Sciences, the East India Marine
`Society, the Royal Academy of Edinburgh, the Royal
`Society of London, the Royal Irish Academy, the American
`Philosophical Society, the Connecticut Academy of Arts
`
`iv
`
`4
`
`

`

`and Sciences, the Boston Marine Society, the Royal
`Astronomical Society, the Palermo Academy of Science,
`and the Royal Academy of Berlin.
`Nathaniel Bowditch outlived all of his brothers and
`sisters by nearly 30 years. He died on March 16, 1838, in
`his sixty-fifth year. The following eulogy by the Salem
`Marine Society indicates the regard in which this distin(cid:173)
`guished American was held by his contemporaries:
`"In his death a public, a national, a human benefactor has
`departed. Not this community, nor our country only, but the
`
`whole world, has reason to do honor to his memory. When the
`voice of Eulogy shall be still, when the tear of Sorrow shall
`cease to flow, no monument will be needed to keep alive his
`memory among men; but as long as ships shall sail, the needle
`point to the north, and the stars go through their wonted
`courses in the heavens, the name of Dr. Bowditch will be
`revered as of one who helped his fellow-men in a time of need,
`who was and is a guide to them over the pathless ocean, and of
`one who forwarded the great interests of mankind."
`
`v
`
`5
`
`

`

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`Original title page of The New American Practical Navigator, First Edition, published in 1802.
`
`vi
`
`6
`
`

`

`PREFACE
`
`The Naval Observatory library in Washington, D.C., is
`unnaturally quiet. It is a large circular room, filled with
`thousands of books. Its acoustics are perfect; a mere
`whisper from the room 's open circular balcony can be
`easily heard by those standing on the ground floor. A
`fountain in the center of the ground floor softly breaks the
`room's silence as its water stream gently splashes into a
`small pool. From this serene room, a library clerk will lead
`you into an antechamber, beyond which
`is a vault
`containing the Observatory's most rare books. In this vault,
`one can find an original 1802 first edition of the New
`American Practical Navigator.
`One cannot hold this small, delicate, slipcovered book
`without being impressed by the nearly 200-year unbroken
`chain of publication that it has enjoyed. It sailed on U.S.
`merchantmen and Navy ships shortly after the quasi-war
`with France and during British impressment of merchant
`seamen that led to the War of 1812. It sailed on U.S. Naval
`vessels during operations against Mexico in the I 840's, on
`ships of both the Union and Confederate fleets during the
`Civil War, and with the U.S. Navy in Cuba in 1898. lt went
`around the world with the Great White Fleet, across the
`North Atlantic to Europe during both World Wars, to Asia
`during the Korean and Vietnam Wars, and to the Middle
`East during Operation Desett Storm. It has circled the globe
`with countless thousands of merchant ships for 200 years.
`As navigational requirements and procedures have
`changed throughout the years, Bowditch has changed with
`them. Originally devoted almost exclusively to celestial
`navigation, it now also covers a host of modern topics. It is
`as practical today as it was when Nathaniel Bowditch,
`master of the Putnam, gathered the crew on deck and taught
`in calculating lunar
`them the mathematics involved
`distances. It
`is that practicality
`that has been the
`publication's greatest strength, and
`that makes
`the
`publication as useful today as it was in the age of sail.
`Seafarers have long memories. In no other profession
`is tradition more closely guarded. Even the oldest and most
`cynical acknowledge the special bond that connects those
`who have made their livelihood plying the sea. This bond is
`not comprised of a single strand; rather, it is a rich and
`varied tapestry that stretches from the present back to the
`birth of our nation and its seafaring culture. As this book is
`a part of that tapestry, it should not be lightly regarded;
`rather, it should be preserved, as much for its historical
`importance as for its practical utility.
`Since antiquity, mariners have gathered available
`navigation information and put it into a text for others to
`follow. One of the first attempts at this involved volumes of
`
`Spanish and Portuguese navigational manuals translated
`into English between about 1550 to 1750. Writers and
`translators of the time "bo1Towed" freely in compiling
`navigational texts, a practice which continues today with
`works such as Sailing Directions and Pilots.
`Colonial and early American navigators depended
`exclusively on English navigation texts because there were
`no American editions. The first American navigational text,
`Orthodoxal Navigation, was completed by Benjamin
`Hubbard in 1656. The first American navigation text
`published in America was Captain Thomas Truxton's
`Remarks, Instructions. and Examples Relating to the
`Latitude and Longitude; also the Variation of the Compass,
`Etc., Etc., published in 1794.
`The most popular navigational text of the late 18th
`century was John Hamilton Moore's The New Practical
`Navigator. Edmund M. Blunt, a Newburyport publisher,
`decided to issue a revised copy of this work for American
`navigators. Blunt convinced Nathaniel Bowditch, a locally
`famous mariner and mathematician, to revise and update
`The New Practical Navigator. Several other learned men
`assisted in this revision. Blunt's The New Practical
`Navigator was published in 1799. Blunt also published a
`second American edition of Moore's book in 1800.
`By 1802, when Blunt was ready to publish a third
`edition, Nathaniel Bowditch and others had corrected so
`many en·o1'S in Moore's work that Blunt decided to issue the
`work as a first edition of the New American Practical
`Navigator. It is to that 1802 work that the current edition of
`the American Practical Navigator traces its pedigree.
`The New American Practical Navigator stayed in the
`Bowditch and Blunt family until the government bought the
`copyright in 1867. Edmund M. Blunt published the book
`until 1833; upon his retirement, his sons, Edmund and
`George, took over publication.The elder Blunt died in
`1862; his son Edmund followed in 1866. The next year,
`1867, George Blunt sold the copyright to the government
`for $25,000. The government has published Bowditch ever
`since. George Blunt died in 1878.
`Nathaniel Bowditch continued to correct and revise the
`book until his death in 1838. Upon his death, the editorial
`responsibility for the American Practical Navigator passed
`to his son, J. Ingersoll Bowditch. Ingersoll Bowditch
`continued editing the Navigator until George Blunt sold the
`copyright to the government. He outlived all of the principals
`involved in publishing and editing the Navigator, dying in
`1889.
`The U.S. government has published some 52 editions
`since acquiring the copyright to the book that has come to
`
`vii
`
`7
`
`

`

`be known simply by
`its original author's name,
`"Bowditch." Since the government began production, the
`book has been known by its year of publishing, instead of
`by the edition number. During a revision in 1880 by
`Commander Phillip H. Cooper, USN, the name was
`changed to American Practical Navigator. Bowditch's
`original method of taking "lunars" was finally dropped
`from the book just after the turn of the 20th century. After
`several more revisions and printings through World Wars I
`and II, Bowditch was extensively revised for the 1958
`edition and again in 1995.
`Recognizing the limitations of the printed word, and that
`computers and electronic media permit us to think about the
`processes of both navigation and publishing in completely
`new ways, NIMA ha~, for the 2002 edition, produced the first
`official Compact Disk-Read Only Memory (CD-ROM)
`version of this work. This CD contains, in addition to the full
`text of the printed book, electronic enhancements and
`additions not possible in book form. Our goal is to put as
`much useful navigational info1mation before the navigator as
`possible in the most understandable and readable fonnat. We
`are only beginning to explore the possibilities of new
`technology in this area.
`As much as it is a part of history, Bowditch is not a
`history book. As in past editions, dated material has been
`dropped and new methods, technologies and techniques added
`to keep pace with the rapidly changing world of navigation.
`The changes to this edition are intended to ensure that it
`remains the premier reference work for modem, practical
`marine navigation. This edition replaces but does not cancel
`fo1mer editions, which may be retained and consulted as to
`historical navigation methods not discussed herein.
`
`PART 1, FUNDAMENTALS, includes an overview of
`the types and phases of marine navigation and the organi(cid:173)
`zations which develop, support and regulate it. It includes
`chapters relating to the types, structure, use and limitations of
`nautical charts; a concise explanation of geodesy and chart
`datums; and a summary of various necessary navigational
`publications.
`PART 2, PILOTING, emphasizes the practical aspects
`of navigating a vessel in restricted waters, using both
`traditional and electronic methods.
`PART 3, ELECTRONlC NAVIGATION, explains the
`nature of radio waves and electronic navigation systems.
`Chapters deal with each of the several electronic methods
`of navigation--satellite, Loran C, and radar, with special
`emphasis on satellite navigation systems and electronic
`charts.
`PART 4, CELESTIAL NAVIGATION, updates the
`former edition with more modem terminology, and discusses
`
`the use of calculators and computers for the solution of celestial
`navigation problems.
`PART 5, NAVIGATIONAL MATHEMATICS,
`remains unchanged from the fonner edition.
`PART 6, NA VJGATIONAL SAFETY, discusses recent
`developments in management of navigational resources, the
`changing role of the navigator, distress and safety communi(cid:173)
`cations, procedures for emergency navigation, and the
`increasingly complex web of navigation regulations.
`PART 7, OCEANOGRAPHY, has been updated to
`reflect the latest science and terminology.
`incorporates
`PART 8, MARINE WEATHER
`updated weather routing information and new cloud
`graphics.
`
`The pronoun "he," used throughout this book as a reference
`to the navigator, refers to both genders.
`The printed version of this volume may be corrected
`using the Notice to Mariners and Summary of Corrections.
`Suggestions and comments for changes and additions may
`be sent to:
`
`NATIONAL IMAGERY AND MAPPING AGENCY
`
`MARITIME SAFETY INFORMATJON DIVISION
`
`MAIL STOP D-44
`
`4600 SANGAMORE RD.
`
`BETHESDA, MARYLAND, 208 16-5003
`
`UNITED STATES OF AMERICA
`
`This book could not have been produced without the
`expertise of dedicated personnel from many government
`organizations, among them: U.S. Coast Guard, U.S. Naval
`Academy, U.S. Naval Oceanographic Office, US Navy
`Fleet Training Center, the U.S. Naval Observatory, Office
`of the Navigator of the Navy, U.S. Merchant Marine
`Academy, U.S. Coast and Geodetic Survey, the National
`Ocean Service, and the National Weather Service. In
`addition to official government expertise, we must note the
`contributions of private organizations and individuals far
`too numerous to mention. Mariners worldwide can be
`grateful for the experience, dedication, and professionalism
`of the many people who generously gave their time in this
`effort. A complete list of contributors can be found in the
`"Contributor's Corner" of the CD-ROM version of this
`book.
`
`THE EDITORS
`
`viii
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`8
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`

`

`TABLE OF CONTENTS
`
`NATHANIEL BOWDJTCH ....................................................................................................................................... .... iii
`PREFACE ................................................................................................................................................................... vii
`
`PART I - FUNDAMENTALS
`
`CHAPTER I.
`CHAPTER 2.
`CHAPTER 3.
`CHAPTER4.
`
`IN TRODUCTION TO MARINE NAVIGATION ............... ,. ..... ,.,.,., ............................ , , ........... ., ...... I
`GEODESY AND DATUMS IN NA VIGATJON .............................................. , ............................ 15
`NAUTICAL CHARTS ................................... : .. .-: ........................ : .... ,, ... , ..... : ............... .-... : . .-..... :.,,.,, ........ ::23
`NAUTICAL PUBLICATION S ...................................................................................................... 51
`
`PART 2 - PILOTING
`
`CHAPTER S.
`CHAPTER6.
`CHAPTER 7.
`CHAPTERS.
`CHAPTER9.
`
`SHORT RANGE AIDS TO NAVIGATION ....... , ..... , ....... , .... , ...... , ................ , ...... ,,., .......... ,,, .......... 63
`COMPASSES ... ::·· .............................. '. ..... , ... , ................. · ......... -., ... '..; .. :.; .... ; ... :; ... :: ... ::: ... _.: .. : .. :·:·:._::._., ...... 8 I
`DEAD RECKONING ........... :-.:.:.; .................... .-..... :-..,. ... ,·;.; ........ ,, ... ~ ...... : ..... :.-........ , ............. :: ... :.: .... 99
`PlL.OTINO .... ,,., ... ,·: .. : ............... ,,·, .... : ...... , ........................... ,:· ... , ... ,, .. ,,.,, .......... : ...... , ...... :.· .... :.: ..... : ............... 105
`TIDES AND TIDAL CURRENTS ... _,, .......... ,, .. , ....... , ....... ,,., ... , ........... ,, ................ , .. ,.., ... , ... , ... , ............. I 29
`
`PART 3 - ELECTRONIC NAVIGATION
`
`CHAPTER I 0. RADIO WAVES ............. _..,. ....... _. ....... , ....................... , .......... :; .......... '..-.-. ... -.-......... : . .-.......... ,, ;.: ... :'.: ... ::::-.·:· 151
`CHAPTER 11. SATELLITE NAVIGATION ........... -.-. ....... : .. ; ... ;; ..... : ......... : ..... : ....... :: ... ; ........... .-.......................... : 163
`CHAPTER 12. LORAN NA V!GATION ............... , ..... : ..... ·: ... :-.:., ... : .... ;· .................. :·::: ............ :.· ....... : .............................. 173
`CHAPTER 13. RADAR NAVIGATION ., .. ,, ... ,, .. , .. ,., .. ,, ........... ,, ....... , ................... , ..... , ....... ,.. ................. , ................... 187
`CHAPTER 14. ELECTRONIC CHARTS ............ , ............................ , ............................................................. , . .-...... 199
`
`PART 4- CELESTIAL NAVIGATION
`
`CHAPTER 15. NAVIGATIONAL ASTRONOMY .............................................................................................. 217
`CHAPTER 16.
`JNSTRUMENTS FOR CELESTIAL NA VI GA Tl ON .,: ...... : .... : ........ ,. ............... : ... · ....... : .............. 26 1
`CHAPTER 17. AZIMUTHS AND AMPLITUDES .............................................................................................. 271
`CHAPTER 18. TIME ............................................................................................................ ................................. 275
`CHAPTER 19. THE ALMANACS .................................... ................................. .................................................. 287
`CHAPTER 20. SIGHT REDUCTION .......................................................................................... ......................... 295
`
`PARTS- NAVIGATIONAL MATHEMATICS
`
`CHAPTER 2 1. NAVIGATIONAL MATHEMATICS ... _, ...... , .. _,_ ....... , ...... , ... ,, .. , ........ , ... , .... , ... .,, ..... , ... ,, ... ., .. , ....... ,, .. 3 17
`CHAPTER 22. CALCULATIONS AND CONVERSIONS ................................................ ;· ........ ;._.:.::.: ... = . ..... : •• , ... 329
`CHAPTER 23. NA VI GA TIONAL ERRORS .......................................... : ... :·: ... :· .... ,,; ......... ~-.: ........ : ........ ;.:· . .-.': ......... 341
`CHAPTER 24. THE SAILIN GS · .. .-........... ,, .......... , ............................................................. :., .................. ,..-....................... -345
`
`PART 6 - NAVIGATIONAL SAFETY
`
`CHAPTER 25. NAVIGATION PROCESSES ....................... _. .. ,,, ...................... ,. ........ , ...... ~. , .. ,_,,., ........ , .... , .... , ........... 363
`CHAPTER 26. EMERGENCY NAVIGATION ......................................................... : .................. : ..... ; ... -.... :.; ...... 373
`CHAPTER 27. NA VJGA TION REGULATIONS .................................... : ............. ; ................................. :.< ...... '. .. 383
`CHAPTER 28. MARITIME SAFETY SYSTEMS ................. : .............................. , ........................................... , : ... 393
`CHAPTER 29. HYDROGRAPHY .. _. ..... ,, .............. , ..................... ,. ........ ........................... , .... _. ... , ...... ,,._.,,, ..... _. .. _._.,,_. ......... 409
`
`ix
`
`9
`
`

`

`PART 7 - OCEANOGRAPHY
`
`CHAPTER30.
`CHAPTER31.
`CHAPTER 32.
`CHAPTER33.
`
`THE OCEANS ........................................................................................................................... 425
`OCEAN CURRENTS ................................................................................................................ 433
`WAVES, BREAKERS AND SURF .......................................................................................... 441
`lCENAVIGATION ................................................................................................................... 453
`
`PART 8- MARINE METEOROLOGY
`
`CHAPTER34.
`CHAPTER35.
`CHAPTER36.
`CHAPTER 37.
`
`WEATHER ELEMENTS ........................................................ , ....................................... , ......... 48 1
`TROPICAL CYCLONES ................... , ...................................................................................... 503
`WEATHER OBSERVATIONS ................................................... , ............................................. 519
`WEATHER ROUTING ............................................................................................................. 545
`
`NAVIGATION TABLES
`
`EXPLANATION OF NAVIGATION TABLES ....................................................................................................... 557
`
`MATHEMATICAL TABLES
`
`TABLE I.
`TABLE2.
`TABLE3.
`TABLE4.
`
`LOGARITHMS OF NUMBERS ................................................................................................. 565
`NATURAL TRIGONOMETRIC FUNCTIONS ....................................................................... 575
`COMMON LOGARITHMS OF TRIGONOMETRIC FUNCTIONS ...................................... 598
`TRAVERSE TABLES ............................................................................................................... 621
`
`CARTOGRAPHIC TABLES
`
`TABLE 5.
`TA