American practical navigator: an epitome of navigation and nautical astronomy (1914)
Bowditch, Nathaniel, 1773-1838, United States. Navy Dept. Bureau of Equipment, Logan, George Wood, 1868-1915 · Washington, Govt. Print. Off. · leaf 159
O. 365. The Sumner Line.—In practice, under the conditions existing at sea, itis never necessary to determine the whole of a circle of equal altitude, as a very smallportion of it will suffice for the purposes of navigation; the position is always knownwithin a distance which will seldom exceed 30… … 152 THE SUMNER LINE. and may be regarded as a straight line. Such a line, comprising so much of the circleof equal altitude as covers the probable limits of position of the observer, is called aSumner line or Line of position. The latter designation has also a more extended meaning, embracing any…
Navigation · Nautical astronomy
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