The American Practical Navigator/Preface

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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 1840’s, on ships of both the Union and Confederate fleets during the Civil War, and with the U.S. Navy in Cuba in 1898. It 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 Desert 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 them the mathematics involved in calculating lunar 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 “borrowed” 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 Navigatorwas 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 errors 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 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 has, 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 information before the navigator as possible in the most understandable and readable format. We are only beginning to explore the possibilities of new technology in this area.

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:


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.

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 modern, practical marine navigation. This edition replaces but does not cancel former 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 organizations 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, ELECTRONIC 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 modern terminology, and discusses the use of calculators and computers for the solution of celestial navigation problems.

PART 5, NAVIGATIONAL MATHEMATICS, remains unchanged from the former edition.

PART 6, NAVIGATIONAL SAFETY, discusses recent developments in management of navigational resources, the changing role of the navigator, distress and safety communications, 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.

PART 8, MARINE WEATHER incorporates updated weather routing information and new cloud graphics.