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  • Formula for Earth radius at any given latitude.

    From [email protected]@21:1/5 to All on Wed Dec 2 12:42:28 2015
    can you explain the "/180*pi" part? I see it obviously works, but what's the reasoning for it?

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  • From Ian Clifton@21:1/5 to [email protected] on Thu Dec 3 12:20:30 2015
    [email protected] writes:

    can you explain the "/180*pi" part? I see it obviously works, but
    what's the reasoning for it?

    I’m not sure of the context of ths question, but surely it’s just converting degrees to radians?
    --
    Ian ◎

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  • From [email protected]@21:1/5 to chuckage on Thu Feb 18 18:04:52 2016
    On Tuesday, February 8, 2011 at 4:13:50 PM UTC-8, chuckage wrote:
    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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    Is the latitude the geodetic latitude or the geocentric latitude?

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  • From [email protected]@21:1/5 to Poster Matt on Fri Jan 12 02:49:53 2018
    On Thursday, January 31, 2008 at 4:54:17 PM UTC-2, Poster Matt wrote:
    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.

    Hello. You could use this online tool.

    https://rechneronline.de/earth-radius/

    It has also the formula for any latitude, so you can create a function.

    If you get the poles and equator radius (6,356.752 km and 6,378.137 km) from this website, you can see you get the same value as you can see in this page https://en.wikipedia.org/wiki/Earth_radius#Global_average_radii.

    So I think the formula is correct!

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