Sumnern.
/ˈsʌmnə/, U.S. /ˈsəmnər/ Nautical.† II. Simple uses.
I. Compounds.
1. As a modifier, often in the genitive. Designating a method, devised by Thomas Sumner on a voyage in 1837, of finding a vessel's position, employing an approximate value of latitude or longitude based on dead reckoning, in conjunction with an astronomical observation, to calculate a number of positions that define a line that must contain the true position. Also: designating a line determined by this method.Now rare except in Sumner line n. at sense 2.
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society > travel > travel by water > directing or managing a ship > [adjective] > method of finding position
Sumner1849
1843 B. Peirce Let. 16 Mar. in T. H. Sumner New & Accurate Method finding Ship's Position (front matter) My dear Bowditch, I have examined Capt. Sumner's processes, and they are founded on perfectly correct principles.]
1849 H. Raper Pract. Navigation & Naut. Astron. (ed. 3) 345 (heading) Position on a line of bearing. [Note] Or ‘Sumner's Method’.
1918 Amer. Math. Monthly 25 417 To find the latitude and longitude of a ship by the Sumner Method, two lines of position must be determined.
1976 P. Kemp Oxf. Compan. Ships & Sea 845 Sumner's position line, a systemized method of finding a ship's position by means of a sight.
2. Sumner line n. a line of position determined by Sumner's method (see sense 1).Cf. position line n. at position n. Compounds.
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1876 Nature 24 Aug. 347/1 The circle on any part of which the ship may be is now commonly called a Sumner circle of equal altitude. The short straight portion of it which in practice is drawn on the working chart, is called a Sumner line.
2007 J. H. Karl Celestial Navigation GPS Age iii. 29 Because Captain Sumner seems to have been the first to realize this fact, the straight-line LOP [= line of position] approximation is sometimes called the Sumner line.
3. A position determined by Sumner's method. Obsolete. rare.
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1924 R. Clements Gipsy of Horn xii. 228 I worked a Sumner, or position by double altitude.
This entry has been updated (OED Third Edition, September 2019; most recently modified version published online March 2022).
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