Gnomonic Projection The theory of this projection is to make a curved line appear and be a straight line on the chart, i.
"Lectures in Navigation"
Ernest Gallaudet Draper
Since all these charts are constructed on the Gnomonic Projection, it is only necessary to join any two points by a straight line to get the curved line or great circle track which your ship is to follow.
"Lectures in Navigation"
Ernest Gallaudet Draper