|On a mercator projection chart, lines of latitude are parallel as are lines of longitude.
||On gnomonic projection charts, meridians converge and lines of latitude are curved.
|A rhumb line course of 040° crosses each meridian (lines of longitude) at the same angle.
||Great circle routes are straight lines and rhumb lines are curved.
|A rhumb line course is used in all coastal navigation. If a passage is over 600 miles it may be quicker to sail a great circle route, in practice this not always practical as winds, currents and weather systems all influence the choice of the best route.
||A great circle is the longest line that can be drawn around the earth. A segment of a great circle is the shortest distance between two points on the earth surface.