Jan,
Following your "angle-radius" theory will probably give you meaningless
values, as you'll have to assume that the globe is a perfect "ball", which
it isn't. For instance, the distance between the poles are less than the
diameter measured at equator. Easy to understand, if you think of the globe
as a soft ball, rotating around an axis through the poles; the centrifugal
force will force the "ball" into a "disk" shape, with the largest
circumference at equator (not the full, scientific explanation, I'm sure)!
Therefore, regarding the "radius", you can't go backwards, calculating from
the equation (1 nm = 1 min). But you can calculate the circumference,
measured over the poles, as 360 x 60 x 1.852 = 40003.2 km. But this is NOT
the same as the circumference around equator, or in any other angle away
from the rotational axis.
Also; note that the equation (1 nm = 1 min) is one NAUTICAL mile = one
LATITUDE minute. This relation is supposed to be exact, as one latitude
minute is simply the definition of a nautical mile.
1 nm = 1.852 km, and (according to my unit conversion program) = 1.150779
mile.
Still, this is no solution to your problem; I'll have to recommend - like
others here - that you find some kind of software for the purpose. Or, if
you only use your GPS within a limited aree, find some generic equations
that are nearly true in this area.
And now a little confession: Initially, after reading your first post
yesterday, I didn't notice that your longitude was WEST (habitual thinking,
as I normally work with northern latitudes / eastern longitudes), so I found
you to be located somewhere in a river valley north-east of Lake Bajkal in
Russia. And I simply couldn't figure out how a river located at an elevation
of 312 m could flow into a lake, located at an elevation of 445 m! Well, I'm
glad you're not there - and so should you be! 😉
regards
Peter
"Jan Nademlejnsky" skrev i en meddelelse
news:6A0CF5E52C0925FDEACD3CDBF36DC71D@in.WebX.maYIadrTaRb...
> That's it! Thank you very much, Peter.
>
> As far as I understand it, latitude, and longitude are angles measured
from
> the center of earth to its surface. What is the radius of the earth taken
in
> this calculation?
> I guess I can go backward and recalculate it from your equation 1 mi = 1
> min.