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 sailing and/or plane:
“Come, cuddle your head on my shoulder, dear,
Your head like the golden-rod,
And we will go sailing away from here
To the beautiful land of Nod.”
—Ella Wheeler Wilcox (18551919)
“In time the scouring of wind and rain will wear down the ranges and plane off the region until it has the drab monotony of the older deserts. In the meantimea two-million-year meantimetravelers may enjoy the cruel beauties of a desert in its youth,....”
—For the State of California, U.S. public relief program (1935-1943)