Calculate Diameter for 2 points(lon, lat )

GeoUtils.java

private static final Double EARTH_RADIUS = 6371D; // KM

    public static Double getDiametro(Double latFirst, Double lonFirst, Double latMiddle, Double lonMiddle) {

        Double dLat = Math.toRadians(latMiddle - latFirst);
        Double dLon = Math.toRadians(lonMiddle - lonFirst);

        Double lat1 = Math.toRadians(latFirst);
        Double lat2 = Math.toRadians(latMiddle);

        Double a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
                Math.sin(dLon / 2) * Math.sin(dLon / 2) * Math.cos(lat1) * Math.cos(lat2);

        Double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
        return EARTH_RADIUS * c;
    }