Jaxie's original "context" was actually simply mathematics. His "planar"
comment was part of the great "3 dimensional vector" discussion, where jaxie
revealed his ignorance in a variety of disciplines. (The ICBM comment was also
from that.)

His actual comment was:

"btw, if vectors are "3 dimensional", just how can they be used at a point on
the Earth's surface (which by definition is planer)."


And on ICBM's:
"An Inter Continental Ballistic Missile is "ballistic" and thus has no
navigation system."


And, of course, jaxie just made up his "answer," and was wrong by a few orders
of magnitude. The difference between a Rhumb Line and a Great Circle route can
be a tenth of a mile on a 120 mile trip, and almost a degree on initial heading
at mid latitudes. Not a great difference, I'd argue that there are difference
aspects of the "non-planar" nature of the ocean that are of more relevance to
the coastal sailor. In fact, one sees the effect on any trip longer than a few
miles.

Of course, near the poles this could be more significant At 70 N, for
instance, to go 100 miles East your heading should be 87.6 degrees.



"JAXAshby" wrote in message
...
bass, **IN THE CONTEXT** given, the difference in distance over 120 nm is
about
0.000872225 miles, or a little over 3 feet.

Oh, I totally understand the differences between planar and spherical
mathematics. I also understand that you are foolish if you think that,
when measuring distances across the earth's surface, there is
absolutely no way that planar math will give you the correct distance.
No more that than in ANY circle. The chord length will ALWAYS be
shorter than the arc length of the same segment. Do you disagree with
this statement? If so, how?