You asked.... makrothen calculates distance this way:
double dist(double lat1, double lon1,
double lat2, double lon2) {
// convert from degrees to rad
double a = lat1 * (PI/180);
double b = lon1 * (PI/180);
double c = lat2 * (PI/180);
double d = lon2 * (PI/180);
// same grid is 100km but we'll calc that later
if((a==c) && (b==d)) return 0;
// yow.
return acos(cos(a)*cos(b)*cos(c)*cos(d)+cos(a) *
sin(b)*cos(c)*sin(d)+sin(a)*sin(c)) * 6378.16;
}
Should give you the dist in km between 2 grids.
The 6378.16 km distance is from the makrothen rules.
Some other calculators use a different value for the
diameter of the earth at the equator. Whatever.
Aren't you glad you asked? :)
/steve n9oh
--- writelog-request@contesting.com wrote:
> From: "Dave W7DPW" <w7dpw@comcast.net>
> I would like to find the formula for calculating the
> distance between
> two gridSquares.
>
> Can some one point me in the right direction ?
>
> Dave W7DPW
>
=====
----------------------------------------------------------
Steve Woodruff, N9OH @ 42.18N 88.34W, sjwoodr@yahoo.com
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