American Practical Navigator
Nathaniel Bowditch (originally)
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If you are going to do any kind of really serious cruising, or voyaging, where you are aboard and traveling for significant periods, you really should have a copy of this aboard. Now a publication of the United States National Imagery and Mapping Agency this was originally written by Nathaniel Bowditch and published in 1802. His book was the first to attempt both a fully accurate and complete system of navigation, and to attempt to present the material in a form that would allow people of even the humblest educational backgrounds to learn even the most complex forms of navigation. Such was his influence that his work has been kept in print and revised all these years. Today’s edition is a thoroughly modern work.
This book is large and very thick. It would be easy to be intimidated by it. However we have found that even people who are absolute beginners often find simply reading along through it teaches them an amazing amount with little frustration or confusion. Therefore this book is not only a complete reference on navigation, but it is a self-teaching system that can be used by the beginner.
Nathaniel Bowditch is a hero of your reviewer. Virtually entirely self-educated himself, he was recognized at an early age as one of the foremost thinkers and scientific writers of his era. Further he believed that essentially everyone had the capacity to learn anything they wanted, if the teachers would only take the time to explain things carefully and properly. This has been a great inspiration to your reviewer, who has always taken the attitude that if a student doesn’t understand something, it is up to the teacher to find a better way to communicate the concept. This has really worked.
I do want to outline what you can learn from this book, but if the reader will forgive another personal note. A number of years ago a gentleman named Nathaniel Bowditch V, a lineal descendent of this first Nathaniel, came to me to teach his daughter to sail at a summer colony where I was the sailing master. I hope that I taught in a manner that her ancestor would have approved, and I have remembered the privilege fondly for many years. My successor in teaching there had the privilege of teaching her younger brother Nathaniel Bowditch VI.
The present work starts off with a section labeled “Fundamentals”, which contains an introduction to marine navigation, a discussion of geodesy and datums in navigation, a review of nautical charts, and a description of the functions of available nautical publications.
The second section is on “Piloting”, that is coastwise navigation, and covers short range aids to navigation, compasses, dead reckoning, piloting, and tides and tidal currents. All in wonderful detail which will help you realize all the marvelous things you can do with a remarkably small suite of navigational tools.
The third section is on “Electronic Navigation”, which starts with the basics on radio waves and how they work, satellite navigation, and navigation techniques using radar. Electronic charts are also discussed. I should mention here that writers can make a pretty good living taking small sections of Bowditch and writing cheerful little magazine articles with a couple of color photos of them at the chart table, radar screen, or holding a sextant.
The fourth section, “Celestial Navigation”, covers the basics of astronomy and its application to navigation. Instruments for celestial navigation are described and we are told how to use them. We are shown how to find compass error using celestial bodies. The use of time in navigation is explained. The various types of almanacs that are available are outlined and we are taught how to get the information we need from them. Finally we are shown how we can use the observations we’ve made, time, the almanac and “Publication 229, Sight Reduction Tables for Marine Navigation” to reduce sights to a position on the earth’s surface. It is also explained that you can use the concise tables for sight reduction in the Nautical Almanac or a calculator to do sight reduction as well. Examples are given and a day’s plot on a position plotting sheet is shown.
The fifth section “Navigational Mathematics” starts off with a section on the basic mathematics of geometry so that we understand the underlying theory of determining geometric relationships. We then learn about the common calculations used in navigation and conversions. Examples would be the basic calculations of speed and distance, distances to the horizon, distances from heights of objects, tide calculations, celestial navigation calculations, temperature conversions, lengths and heights of seas, etc. This is all followed by a large number of conversion factors for areas, astronomy, chart work, Earth characteristics, length, mass, mathematics, meteorology, pressure, speed, volume, volume, mass, etc. One of my favorite chapters is on navigational error not so much for the contents as for the concept. You really need to think about how much you can be off in a given situation and take that into account. This sections gives a decent stab at explaining error. The final chapter in this section discusses how to figure in the shape of the Earth in calculating long distance voyages and positions. This is quite fascinating and a knowledge of it will help the average navigator reduce their errors and the times from one place on the globe to another.
The sixth section is on “Navigational Safety”. The first chapter in this section is probably the least useful for yachtsmen in the whole book, in that it is all about organizing the duties of the “navigational team” aboard large ships. On the other hand the second chapter on “emergency navigation” is very interesting. It outlines the minimum you should have to navigate and shows you how to create your own plotting sheets, which are used to work out your dead reckoning and your celestial sites and reconciling the two without trying to do it all at an inconvenient scale on your charts. It then goes on to describe what may look like emergency navigation to a large ship but actually is a pretty good outline of the procedure on a family yacht and even includes how to make a couple of types of astrolable and a cross staff for measuring altitude in case your sextant is damaged irreparably. The chapter on ship routing systems is most valuable for its explanation of the Automatic Identification System, which is beginning to find its way from large ships to family sized yachts. Some people have found this quite helpful though it is very clear that you should have a good working knowledge of the prediction of ship behavior and positions, especially at night, before you should attempt to add on the information provided by AIS. This is followed by information on various safety communications systems mostly useful to the family yacht for its information on Emergency Position Indicating Radio Beacons or “EPIRBs”.
The seventh section is titled “Oceanography” is extremely valuable in understanding the nature and behavior of the sea, especially including the behavior of ocean currents, waves, etc. Also there is a good section on ice navigation which I hope I’ll never need.
The 8th section is on “Marine Meteorology”. There is a lot of good solid information here. I especially recommend reading and re-reading the chapter on Tropical Cyclones. You can do a tremendous amount to avoid or mitigate the worst of the effects of these storms if you understand how they operate. With a thorough understanding of this section and a couple of the Pardey’s book “Storm Tactics Handbook” you’ll be likely to have a lot easier time of it at sea than those who don’t understand what’s going on. The chapter on weather observation is extremely valuable. Far too many sailors today will rely on weather reports for near range prediction when a few simple instruments and some knowledge will give you a lot more information about the near term possibilities. Simple sensitivity to weather signs and attention to the barometer will frequently have you seeking shelter or preparing for a storm well before it actually gets to you, while a weather forecast may be telling you that everything is great even while all hell is breaking loose around you. I feel that their color pictures illustrating the predictive capacity of cloud patterns are particularly helpful. It is an awfully good idea to realize that the sky is telling you what is going to happen as plain as paint, rather than just saying “those clouds look pretty”. The last chapter in this section is on weather routing. For yachts this mostly means studying the climatological data to choose a route and time of year likely to give you the best passage. We’ll happily stay in a nice cruising ground for six months or more waiting for the ideal time to make a passage, and it is well worth it to do so. The primary tool here will be your atlas of pilot charts. As long as we are discussing this it is worth mentioning that recently we have heard people singing the praises of weather routing services and there is no doubt that this can be of value to very large ships which have the speed to actually avoid weather systems. However recently people have put forth the idea that yachts can “avoid” bad weather if they just can sign up for the right “routing service”. This really isn’t true and can lead to people thinking they need not be fully prepared for bad weather. Stay away from that sort of thinking.
The rest of this very thick book, about a third of it, is a large collection of tables all carefully organized and of great use when you need them. Listing all of them would be tedious, but sometimes just knowing the information is there is extremely helpful and quite a relief when you need to solve a given problem. For instance a circular position line showing how far you are from an object of known height can be extraordinarily helpful and even vital in knowing if you can avoid dangers, yet it can be just a matter of knowing how to enter a given table with the right numbers to get a distance off.
All in all, while this isn’t a book you are going sit down and read through in a couple of evenings, it is enormously comforting to take a chapter at a time and make sure you understand it. Gradually a feeling that you’ve really gotten a much better grasp on being a competent mariner steals over you and gives you great satisfaction.
We highly recommend reading this book and keeping it aboard your boat. ™
($49.95, 879 pages, generously illustrated with line art and photographs.)