File: distance.c

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#include "gis.h"

double distance (double east, double west)
{
    double incr;
    double meters;
    double e1, e2;

/* calculate the distance from east edge to west edge at north==0.0
 * for lat-lon this will be along equator. For other databases the
 * north value will make no difference
 *
 * Note, must do lat-lon in 3 pieces, otherwise distance "line" may
 * go the wrong way around the globe
 */
    G_begin_distance_calculations();

    if (east < west)
    {
	double temp;
	temp = east;
	east = west;
	west = temp;
    }

    incr = (east - west) / 3.0 ;
    e1 = west + incr;
    e2 = e1 + incr;

    meters = G_distance (west, 0.0, e1, 0.0) +
	     G_distance (e1, 0.0, e2, 0.0)   +
	     G_distance (e2, 0.0, east, 0.0);

    return meters;
}