CREATE  Function [dbo].[Earth_Radius](@Latitude numeric(9,6))
/*
www.prlsoftware.com
Author: Philip Leitch
Date: 2010
Purpose: This function determines the Earth's Radias at a specific latitude.
Copyright: Philip Leitch 2010
Licensing: This code may be used or modified but if the code is included in a software package attribution to me must be made.
Liability: The developer assumes all liability when using this code.
Notes:
*/
returns float
as
begin
   
    declare @Return as float

    Declare @a as float
    declare @b as float
    set @a = 6378.1370 --Equatorial radius
    set @b = 6356.7523 --Polar radius
    Declare @LatitudeRadians float
    --Convet to radians
    set @LatitudeRadians = @latitude * (pi()/180)   
    set @Return = sqrt(
            (power(power(@a, 2)*Cos(@Latitude),2) + power(power(@b, 2)*sin(@Latitude),2))
                                /
            (power(@a*Cos(@Latitude),2) + power(@b*sin(@Latitude),2))
                )
    return @Return
end