Patent ID: 8365425

Claim:
A navigational plotter for use with a selected navigational chart, the plotter comprising: a generally transparent elongated planar straight edge member having each of a first and a second straight edges parallelly disposed opposite one another bounding a generally rectangular interior surface, a printed central axis bisecting the rectangular interior surface and arranged to be parallel to each of the first and second straight edges; at least one compass rose arranged to have its North/South ordinal points to lie upon the printed central axis; a plurality of instances of a first distance scale being calibrated in accord with the scale of the selected chart along a selected line of latitude, one instance of the first distance scale being printed to span the East/West ordinal points on the at least one compass rose and a second instance of the first distance scale being printed along the first straight edge; a second distance scale being calibrated in accord with the scale of the selected chart along a selected segment of a line of longitude according to a Mercator projection of the selected chart, an instance of the second scale being printed along the second straight edge; and a magnetic North indicator printed upon the rectangular interior surface to intersect the central axis at one instance of the at least one compass rose and to be angularly displaced from the central axis by an angle equivalent to a derived magnetic declination on a selected date.