question: public double greatCircleDistance ( Location location ) { if ( location == null ) { throw new IllegalArgumentException ( Logger . logMessage ( Logger . ERROR , "Location" , "greatCircleDistance" , "missingLocation" ) ) ; } double lat1Radians = Math . toRadians ( this . latitude ) ; double lon1Radians = Math . toRadians ( this . longitude ) ; double lat2Radians = Math . toRadians ( location . latitude ) ; double lon2Radians = Math . toRadians ( location . longitude ) ; if ( lat1Radians == lat2Radians && lon1Radians == lon2Radians ) { return 0 ; } double a = Math . sin ( ( lat2Radians - lat1Radians ) / 2.0 ) ; double b = Math . sin ( ( lon2Radians - lon1Radians ) / 2.0 ) ; double c = a * a + Math . cos ( lat1Radians ) * Math . cos ( lat2Radians ) * b * b ; double distanceRadians = 2.0 * Math . asin ( Math . sqrt ( c ) ) ; return Double . isNaN ( distanceRadians ) ? 0 : distanceRadians ; }
target:  Computes the angular distance of the great circle path between this location and a specified location. In radians, this angle is the arc length of the segment between the two locations. To compute a distance in meters from this value, multiply the return value by the radius of the globe. This function uses a spherical model, not elliptical.