thanks to all!

The penny has dropped.


"Julian Scarfe" wrote in message
...
"xerj" wrote in message
...
If you had a WAC chart that displayed the entire Northern Hemisphere on
one
chart, you could draw a straight line from Los Angeles to New York.
Wouldn't
this be a great circle? And if it is, why couldn't you just fly the
single
heading of that line?

If the other answers haven't done it for you, here's another angle. Look
carefully at the meridians (lines of longitude) on a WAC chart and note
that
they are not quite parallel. You measure your track by the angle between
the straight line you drew and the meridian representing north. So if
they're not parallel, your straight line will cross them at slightly
different angles.

Julian Scarfe