can you explain the "/180*pi" part? I see it obviously works, but
what's the reasoning for it?
chuckage had written this in response to http://www.psjournal.com/gis/Re-Formula-for-Earth-radius-at-any-given-latitude-3623-.htm
:
Uffe Kousgaard wrote:
-------------------------------------
-----------------------------------------------------------------------------
function Radius(Latitude : Degrees;
Spheroid : Spheroid_Type) return Meters is
e2 : long_float renames Models(Spheroid).Eccentricity_Squared;
b : Meters renames Models(Spheroid).Semi_Minor_Axis;
f : long_float renames Models(Spheroid).Flattening;
boa : long_float := 1.0 - f;
Phi : Radians := Deg_to_Rad(Latitude);
Psi : Radians := Geocentric_Latitude(Phi, boa);
cl : long_float;
r : Meters;
begin
cl := cos(Psi);
r := b/sqrt(1.0 - e2*cl**2);
return r;
end Radius;
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The thread 'distance between lon and lat', at the end of last year, was interesting. Those with an interest in the subject might want to look at
the Haversine Formula on the page linked below. I can't remember if this
was mentioned in the thread or not, the thread is so long it'll take ages
to check, and my useless newsgroup software won't let me search!
Haversine Formula:
http://www.movable-type.co.uk/scripts/gis-faq-5.1.html
My question is slightly different. The mean radius of the Earth is approx. 6,372 km, but what formula is used to calculate the radius of the Earth
for any given latitude?
I wish my trig was up to working this out but I'm just a humble computer scientist with no degree in math.
Thank you all for any help in this.
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