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:
“Even though I had let them choose their own socks since babyhood, I was only beginning to learn to trust their adult judgment.. . . I had a sensation very much like the moment in an airplane when you realize that even if you stop holding the plane up by gripping the arms of your seat until your knuckles show white, the plane will stay up by itself. . . . To detach myself from my children . . . I had to achieve a condition which might be called loving objectivity.”
—Anonymous Parent of Adult Children. Ourselves and Our Children, by Boston Women’s Health Book Collective, ch. 5 (1978)
“Theologians should not be ashamed to admit that they cannot enter a contest with such antagonists [the sceptics], and that they do not want to expose the Gospel truths to such an attack. The ship of Jesus Christ is not made for sailing on this stormy sea, but for taking shelter from this tempest in the haven of faith.”
—Pierre Bayle (1647–1706)