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American Practical Navigator by Bowditch

American Practical Navigator by Bowditch

Nathaniel Bowditch published the American Practical Navigator in 1802, calling it an “epitome of navigation”. The first edition focused on celestial navigation, using a watch, sextant and knowledge of astronomy to calculate a position fix. The text has been updated through the years as navigational technology and procedures have evolved.

A remarkable scholar, Nathaniel Bowditch served as a ship’s master and had an exceptional talent for mathematics. Bowditch simplified several procedures for calculating astronomical distances and found many errors in the leading navigational text of the period, The Practical Navigator written by John Moore.

In this world of GPS monitoring dependence, most mariners lack the situational awareness shown by earlier sailors who used nautical charts, a compass, dead reckoning, and navigational astronomy to determine their vessel’s position on the earth. Many modern boaters would be lost or at least confused, if their electronic positioning equipment failed. Bowditch’s work continues to be relevant and the text remains an important marine navigational reference among professional mariners.

The American Practical Navigator

The printed version of Bowditch’s text makes for a substantial book and has been kept current since it was first published in the 1800’s. An up to date copy can be purchased from numerous sources. While available online, many mariners absolutely insist on having a physical copy of The American Practical Navigator at hand.

The American Practical Navigator is known by most mariners as Bowditch and is broken into eight different parts or topics. A series of exhaustive tables follows the main text covering the topics of mathematics, cartography, piloting, celestial navigation, and meteorology. The text has an extensive glossary and is indexed.

Fundamentals: This beginning section of the text describes the types of navigation that can be used by a navigator. They range from dead reckoning to celestial navigation to satellite navigation. The earth isn’t a perfectly shaped sphere and representing it on a flat surface is problematic. Bowditch describes systems of geodetic survey and provides an overview of the global coordinate system. Nautical charts and publications are discussed in this portion of the text.

Piloting: This part of the text is concerned with short range navigation, known as pilotage. It covers navigational aids like lights, buoys, beacons, and marking systems. Use of magnetic and gyroscopic compasses is discussed. The concept of dead reckoning, noting the effects of tides, winds and currents is detailed.

Electronic Navigation: This section didn’t exist in Bowditch’s day. Principals of radio navigation are presented and systems like GPS monitoring, Loran, radar and electronic charts are described.

Celestial Navigation: In this part of the text, Bowditch details navigational astronomy and the instruments needed for celestial navigation. Principals of time, use of the almanacs and sight reduction are presented.

Navigational Mathematics: This section isn’t for the faint of heart or those with an aversion to math. Here Bowditch covers geometry, trigonometry, calculations, conversions, navigational errors and “The Sailings”. Mathematical solutions for finding the course and distance between distant points are known as “The Sailings”.

Navigational Safety: In this part of the Navigator, navigational processes related to emergencies and marine safety are discussed. Safety systems and hydrography are also presented.

Oceanography: The state of the ocean, its currents, waves and surf effect navigation. Ice navigation is covered as well.

Marine Meteorology: In this last section, Bowditch talks about weather elements that impact navigation. Topical chapters cover topical cyclones, observations and weather related routing.

Having a physical copy of American Practical Navigator by Bowditch is something that has been appreciated by many sailors. It represents a wealth of knowledge and makes a connection for mariners with navigational practices and knowledge that have been passed on to the generations. While available for free online, printed copies can be obtained at a modest cost.

NOAA Online Marine Charts

We have discussed GPS monitoring and Principles of Navigation at Boating and Sailing. Modern GPS chart plotters are based on just that, a marine chart published by NOAA. Any serious student of coastal navigation will become familiar with the marine charts published for their areas of operation. The National Oceanographic and Atmospheric Administration (NOAA) operates survey vessels that regularly map the ocean bottom and produce detailed charts for use by mariners.

The first thing you should remember is that boaters use charts, not maps. Charts describe controlling depths, display location of navigation aids, list hazards, and point out key navigational features. The level of detail and information presented is incomparable to an automotive roadmap. Charts are meant to be drawn on and used to document your voyages. A well-used chart will be loaded with notes, past track lines, waypoints, and published updates provided for the chart. A marine chart is a living document, used much like a diary.

Paper charts are sold through a chain of dealers approved by NOAA. They are relatively expensive and hard to use within the confines of a small vessel. Your modern GPS monitoring chart plotter uses a digital version of a NOAA chart to provide you with navigational directions. Recently NOAA has come on-line with about a thousand charts covering Alaska, the Great Lakes, and Atlantic, Gulf, and Pacific Coasts. These on-line charts are a great reference for boaters. View the on-line version of the chart for your operating area, and then compare it to your GPS monitoring display. You will be surprised at the level of detail often missing on chart plotting devices. Being more familiar with the chart of your normal operating area will make using your GPS monitoring tracker that much easier.

Visit the NOAA Office of Coast Survey to view marine charts on-line for areas of interest to you. Remember that there are some operators of regulated commercial vessels required by law to carry a current paper chart onboard. Great resources on charts are the Nautical Chart User’s Manual and Chart No. 1 published by NOAA. Chart No. 1 is a reference that shows all the symbols, abbreviations, and terms used on NOAA marine charts.


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