Thanks to the many people who replied to my question.
I appreciate the suggestions to use a scripting language, spreadsheet, etc., but for my simple needs that would be like taking an 18-wheel truck to pick up a few groceries. All I need is a program to do an occasional simple diagram in SVG. It wouldn't necessarily be a plot of a ship's course. That was just an typical example. Basically, I need to do some light duty drafting. But I get the feeling that Inkscape is targeted more at artwork than technical illustration.
Erik wrote:
What I, and I presume Paul want to do is plot surveys like the following:
Point Point Distance (metres) Bearing (degrees) A B 60 7 B C 80 45 C D 85 133 D E 100 35
We want to plot A->B and then B->C etc to the end of the series.
That's the idea. What I have in mind: a virtual straightedge which can be snapped to a selected node, then rotated about that point to any desired orientation. Rotation can be done by eye, and also by inputting a numeric value. The 0 degree orientation can be vertical or horizontal at the user's option. In addition, the straightedge can be snapped to any straight line that contains the pivot node, then rotated relative to that direction.
The pen's movement is constrained to follow the straightedge. Or, the user can specify the start and end points of a line in terms of distance along the straightedge, the pivot node acting as the zero point of the distance scale.
All that may sound elaborate, but it's nothing more than what you can do with a protractor and ruler.