Position Finding By The Improved Sumner Method

Author : H. S. Blackburne
Publisher : Forgotten Books
ISBN 13 : 9780267889945
Total Pages : 84 pages
Book Rating : 4.8/5 (899 download)

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Download or read book Modern Up-to-Date Navigation written by H. S. Blackburne and published by Forgotten Books. This book was released on 2018-02-06 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from Modern Up-to-Date Navigation: Position Finding by the Improved "Sumner" Method Contrasted With the New Navigation (Marcq St. Hilaire System), And the Old "Sumner" Method The principal object of the publication of the following notes on practical modern navigation and the extracts and supplementary tables from our books of Nautical Tables is for the purpose of drawing more prominent attention to the great value and importance of the problem for finding the ship's position at twilight from the observa tion of two or three stars. The great value of this problem in navigation was much impressed on the writer through his continued practice of it during several years of his sea life-and the very general neglect of it by the majority of navigators has impelled him to do all in his power during the last thirty and odd years to bring this problem into the regular practice of navigators, so far, he has to admit, without much success. He has long been strongly of'the opinion, which has been further impressed on him by the investigation of more than one shipping inquiry case held in New Zealand, that a general practice of this observation would be the means of saving many ships from disaster. Two shipmasters have already thanked him, one by letter and the other verbally, for impressing the value of stellar observations on them through his books, and stating that through this their ships had been saved from great risk of being lost through stranding. Although our tables are entitled Azimuth and Reduction Tables, and they have been acknowledged as such - to be the most complete and comprehensive tables yet published - the principal purpose of them, in the author's mind, was for facilitating the problem of determining the ship's position from two observations out of the meridian, and especially with the view of making this problem particularly easy for star-work. No doubt they have encouraged, and will yet more do so, a small minority of navigators to take up this problem, but he is now firmly convinced that it will never become a general practice among ship officers till the problem is given in the Board of Trade examinations for masters and mates, and candidates are allowed the use of such tables and methods as they have been in the habit of using to help them in solv ing the problem. The problem is already given in the Board of Trade examination for extra master, but it is set in a way which I presume would never occur in actual practice, requiring two observers with sextants and another person to take the time, and both observers must take their observation at the exact same instant of time, and the problem is then required to be worked by a very lengthy process, which does not always give an accurate result (see example, page The outcome of this is to leave an impression on the mind of the candidate that the problem is too long a business for ordinary practice, and in consequence is very generally dropped after he leaves the examination-room. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.