The rhumbline is a straight line drawn on a chart (or at least that's my
intuitive definition; I'm not sure what the formal definition is).

If I'm not mistaken, a rhumb line is a line that crosses all meridians
at the same angle.

So a rhumb line is not a straight line on a sectional chart, except in
a few special cases (e.g., the equator). Notice that on the chart
Kyler posted, the meridians are closer together at the top of the
chart than at the bottom, so that straight line crosses each meridian
ast a slightly different angle.

Of course, once you get into the whole concept of representing the surface
of a sphere(oid) on a flat piece of paper, and the different chart
projections used to do it, the definition of "a straight line" becomes a
little hard to pin down.

I don't see why. A straight line is one that can be drawn using a
straightedge. As Euclid would say, it's the shortest distance between
to points on the chart. I believe one reason the Lambert chart was
invented was to make it possible to use a straightedge to draw a great
circle route.

vince norris