__Terms for Plotting:__

__E:__ position drawn so that the vector E-R represents your own course and speed

__R:__ the initial position of the plotted object

__M:__ the second/final position of the plotted object

__E-R:__ "OuR," our course and speed. More exactly, a leg of the plotting triangle that is as
long as our distance run between plots and running along the course we are heading

__E-M:__ "ThEM," the course and speed of the other guy. More exactly, a leg of plotting triangle
as long as the distance the other vessel ran between plots and running along their true course

__R-M:__ "Relative Motion Line," displays the relative motion between you and the other vessel