经纬度计算两点距离

/**
	 * 计算两点之间的距离,单位/m
	 */
	public static double distance(double long1, double lat1, double long2,  
	        double lat2) {  
	    double a, b, R;  
	    R = 6378137; // 地球半径  
	    lat1 = lat1 * Math.PI / 180.0;  
	    lat2 = lat2 * Math.PI / 180.0;  
	    a = lat1 - lat2;  
	    b = (long1 - long2) * Math.PI / 180.0;  
	    double d;  
	    double sa2, sb2;  
	    sa2 = Math.sin(a / 2.0);  
	    sb2 = Math.sin(b / 2.0);  
	    d = 2  
	            * R  
	            * Math.asin(Math.sqrt(sa2 * sa2 + Math.cos(lat1)  
	                    * Math.cos(lat2) * sb2 * sb2));  
	    return d;  
	}