This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 Excerpt: ...is the same as the latitude of the point on the line A', R/J 25 19'.4 S. B115 31.5 W. We now have two Sumner linee, A'and B', under Case I, whose common latitude is 25 19MS., and whose longitudes on the common parallel are 114 61K.7 and 115 31'.5. Hence, the difference of longitude on the common parallel is 115 31'.5 W. 114 59'.7 W. CHAPTER XVI. THE PEAOTIOE 01 NAVIGATION AT SEA. 381. Having set forth in previous chapters the methods of working dead reckoning and of solving problems to find the latitude, longitude, chronometer correction, and azimuth from astronomical observations, it will be the aim of the present chapter to describe the conditions which govern the choice and employment of the various problems, together with certain considerations by which the navigator may be guided in his practical work at sea. 382. Departure And Dead Reckoning.--On beginning a voyage, a good departure must, be taken while landmarks are still in view and favorably located for the purpose; this becomes the origin of the dead reckoning, which, with frequent new departures from positions by observation, is kept up to the completion of the voyage, thus enabling the mariner to know, with a fair degree of accuracy, the position of his vessel at any instant. At the moment of taking the departure, the reading of the patent log (which should have been put over at least long enough previously to be regularly running) must be recorded, and thereafter at the time of taking each sight and at every other time when a position is required for any purpose, the log reading must also be noted. It is likewise well to read the log each hour; for general information as to the speed of the vessel as well as to observe that it is in proper running order and that the rotator has not been fouled ...

The American Practical Navigator, first published in 1802, was billed as the "epitome of navigation" by its original author, Nathaniel Bowditch. The text has evolved with the advances in navigation practices since that first issue and continues to serve as a valuable reference for marine navigation in the modern day. The publication describes in detail the principles and factors of navigation, including piloting, electronic navigation, celestial navigation, mathematics, safety, oceanography and meterology. It also contains various tables used in typical navigational calculations and solutions, including the formulas used to derive the tabular data. - NGA

The Sight Reduction Tables for Marine Navigation (Pub 229) is published in six volumes, each of which contains two-eight degree zones of latitude with a one-degree overlap between volumes. They are designed to facilitate the practice of celestial navigation at sea. The tables are primarily used with the intercept method of sight reduction by entering arguments of latitude, declination, and local hour angle and obtaining tabulated altitudes and azimuth angles. The tables are prepared and published by NIMA on an as-needed basis.

This book is a compilation of all the formulae that a mariner is commonly called upon to use but the exact workings of which he has perhaps forgotten. For each subject category, the author states the basic parameters in narrative form, often including a figure, graph, chart, diagram, or table, and then provides accompanying equations and their amplifications. Although some formulae that are simpler in format are propounded in other texts, many of those formulae lead to confusion in that “special rules†must be applied to them in order to obtain a correct answer. However, the rules applied to the formulae in this book work for all problems. In a great circle sailing situation, for example, the fact of whether the vertex is ahead of you or behind you does not matter—if you apply the rule(s) given in this book, you will get the correct answer. Another important feature of the book is its devotion of over ten pages of material to the international system of units (S.I.)