Plane sailing (also spelled plain sailing) is an approximate method of navigation over small ranges of latitude and longitude. With the course and distance known, the difference in latitude ΔφAB between A and B can be found, as well as the departure, the distance made good east or west. The difference in longitude ΔλAB is unknown and has to be calculated using meridional parts as in Mercator Sailing.
Both spellings ("plane" and "plain") have been in use for several centuries,
Plane sailing is based on the assumption that the meridian through the point of departure, the parallel through the destination, and the course line form a right triangle in a plane, called the "plane sailing triangle".
The expression "plane sailing" has, by analogy, taken on a more general meaning of any activity that is relatively straightforward.
Famous quotes containing the words plane and/or sailing:
“with the plane nowhere and her body taking by the throat
The undying cry of the void falling living beginning to be something
That no one has ever been and lived through screaming without enough air”
—James Dickey (b. 1923)
“I saw three ships come sailing by,
Come sailing by, come sailing by,
I saw three ships come sailing by,
On Christmas Day in the morning.”
—Unknown. As I Sat on a Sunny Bank. . .
Oxford Book of Light Verse, The. W. H. Auden, ed. (1938)