Sumner Line

Sumner line

[′səm·nər ‚līn]
(navigation)
A line of position established by the Sumner method.
Any celestial line of position (deprecated usage).

Sumner Line

 

a celestial line of position established by the Sumner method. Sumner lines are straight lines of equal altitude and are widely used in navigation to determine the position of a ship or airplane through observations of the altitudes of celestial bodies.

References in classic literature ?
Both the captain and mate worked out the position on a Sumner line, and agreed, and at noon agreed again, and verified the morning sights by the noon sights.
Captain Doane worked hard, pursuing the sun in its daily course through the sky, by the equation of time correcting its aberrations due to the earth's swinging around the great circle of its orbit, and charting Sumner lines innumerable, working assumed latitudes for position until his head grew dizzy.