midpoint between two latitude and longitude

Question

I am trying to convert the code snippet given in this http://www.movable-type.co.uk/scripts/latlong.html into java. But I am not getting same result as that of site. Here is my code to find the midpoint between two points where their latitudes and longitudes are given

midPoint(12.870672,77.658964,12.974831,77.60935);     public static void midPoint(double lat1,double lon1,double lat2,double lon2)     {    double dLon = Math.toRadians(lon2-lon1);         double Bx = Math.cos(lat2) * Math.cos(dLon);         double By = Math.cos(lat2) * Math.sin(dLon);         double lat3 = Math.atan2(Math.sin(lat1)+Math.sin(lat2),Math.sqrt( (Math.cos(lat1)+Bx)*(Math.cos(lat1)+Bx) + By*By) );         double lon3 = lon1 + Math.atan2(By, Math.cos(lat1) + Bx);         System.out.print(lat3 +" " + lon3 );     } 

I am not sure whethe dLon is correct or not. So please help me guys to figure it out. P.S.I need to find the latitude and longitude of the midpoint

Answer 1

You need to convert to radians. Change it to the following:

public static void midPoint(double lat1,double lon1,double lat2,double lon2){      double dLon = Math.toRadians(lon2 - lon1);      //convert to radians     lat1 = Math.toRadians(lat1);     lat2 = Math.toRadians(lat2);     lon1 = Math.toRadians(lon1);      double Bx = Math.cos(lat2) * Math.cos(dLon);     double By = Math.cos(lat2) * Math.sin(dLon);     double lat3 = Math.atan2(Math.sin(lat1) + Math.sin(lat2), Math.sqrt((Math.cos(lat1) + Bx) * (Math.cos(lat1) + Bx) + By * By));     double lon3 = lon1 + Math.atan2(By, Math.cos(lat1) + Bx);      //print out in degrees     System.out.println(Math.toDegrees(lat3) + " " + Math.toDegrees(lon3)); }