| 释义 |
Sumner2|ˈsʌmnə(r)|
The name of Thomas H. Sumner (1807–76), U.S. shipmaster, used attrib., in the possessive, and absol., with reference to a method devised by him in 1837 of finding one's position on the surface of the earth, 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; so Sumner line = position line s.v. position n. 7 b.
1849H. Raper Pract. of Navigation & Naut. Astron. (ed. 3) 345 (heading) Position on a line of bearing. [Note] Or ‘Sumner's Method’. 1881S. T. S. Lecky ‘Wrinkles’ in Pract. Navig. ii. viii. 201 Unless the error of the latitude is greater than that assumed, the ship must be somewhere on this ‘Line of position’, which, for convenience, will henceforth in these pages be termed a ‘Sumner line’, after the American seaman who first brought this useful problem prominently to the notice of the profession. 1901J. R. Walker Explanation of ‘New Navigation’ 8 The straight line is called the Sumner Line, or Line of Position. 1919[see position n. 7 b]. 1924R. Clements Gipsy of Horn xii. 228, I worked a Sumner, or position by double altitude. 1976Oxf. Compan. Ships & Sea 845 Sumner's position line, a systemized method of finding a ship's position by means of a sight. |