Calculate distance between two locations in metre

Question

I have two locations and I want to calculate distance in meter. I wrote some code but it's not working perfectly.

private void getDistanceBetweenTwoPoints(double lat1,double lon1,double lat2,double lon2)
{
    Location loc1 = new Location("");
    loc1.setLatitude(lat1);
    loc1.setLongitude(lon1);

    Location loc2 = new Location("");
    loc2.setLatitude(lat2);
    loc2.setLongitude(lon2);

    int R = 6371; // km

    double dLat = deg2rad(lat2-lat1);
    double dLon = deg2rad(lon2-lon1);
    double  a =
            Math.sin(dLat/2) * Math.sin(dLat/2) +
                    Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) *
                            Math.sin(dLon/2) * Math.sin(dLon/2)
            ;
    double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    double distanceInMeters = R * c;
    Log.e("distanceInMeters",distanceInMeters/10000+"mm");
}

public double  deg2rad(double deg) {
    return deg * (Math.PI/180);
}

How can I calculate distance in meter? My goal is, if meter > 200 do something. How can i solve my problem?

Answer 1

There is no need to re-invent the wheel for this.

You can just use the Location.distanceBetween() method.

From the documentation:

Computes the approximate distance in meters between two locations

Here is a simple example:

private float getDistanceBetweenTwoPoints(double lat1,double lon1,double lat2,double lon2) {

    float[] distance = new float[2];

    Location.distanceBetween( lat1, lon1,
            lat2, lon2, distance);

    return distance[0];
}

If the result array has more than just index zero populated, the other indices each contain a bearing (initial and final).

A bearing is a number that specifies a compass direction.

From http://www.geomidpoint.com/destination/help.html :

The bearing (or azimuth) is the compass direction to travel from the starting point, and must be within the range 0 to 360. 0 represents north, 90 is east, 180 is south and 270 is west.