how to find the distance between two geopoints?

double distance;  

Location locationA = new Location("point A");  

locationA.setLatitude(latA);  
locationA.setLongitude(lngA);  

Location locationB = new Location("point B");  

locationB.setLatitude(latB);  
LocationB.setLon开发者_StackOverflow中文版gitude(lngB);  

distance = locationA.distanceTo(locationB);  

the above code is not working and i am getting 0.0 Km as distance? Also in the constructor of the location class, what does the string provider mean. In the above code i am using PointA and PointB as the providers.

why is the above code not working?

thank you in advance.

LOGCAT 05-09 17:48:56.144: INFO/current loc(1573): lat 0.0 lng 0.0 05-09 17:48:56.155: INFO/checklocation loc(1573): lat 54.4288665 lng 10.169366

Just a quick snippet since I didn't see a complete and simple solution with GeoPoints above:

public float getDistanceInMiles(GeoPoint p1, GeoPoint p2) {
    double lat1 = ((double)p1.getLatitudeE6()) / 1e6;
    double lng1 = ((double)p1.getLongitudeE6()) / 1e6;
    double lat2 = ((double)p2.getLatitudeE6()) / 1e6;
    double lng2 = ((double)p2.getLongitudeE6()) / 1e6;
    float [] dist = new float[1];
    Location.distanceBetween(lat1, lng1, lat2, lng2, dist);
    return dist[0] * 0.000621371192f;
}

If you want meters, just return dist[0] directly.

Try Location.distanceBetween(..)

Update:

If you are getting lat/lon from GeoPoint then they are in microdegrees. You must multiply by 1e6.

As stated above, the Location Class is the way to go. Here is the code I have used :

Location locationA = new Location("point A");

locationA.setLatitude(pointA.getLatitudeE6() / 1E6);
locationA.setLongitude(pointA.getLongitudeE6() / 1E6);

Location locationB = new Location("point B");

locationB.setLatitude(pointB.getLatitudeE6() / 1E6);
locationB.setLongitude(pointB.getLongitudeE6() / 1E6);

double distance = locationA.distanceTo(locationB);

In this example, both pointA and pointB are instances of the GeoPoint class.

This is not an answer, but note the signature for the Location constructor is Location(String provider).

i.e. the String you pass to the constructor should be one of LocationManager.GPS_PROVIDER, LocationManager.NETWORK_PROVIDER or LocationManager.PASSIVE_PROVIDER, not "point A" and "point B".

An alternative way to accomplish the above,

    public class Distance {

    public static double distance(double lat1, double lon1, double lat2, double lon2) {

        double theta = lon1 - lon2;

        double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2))
                + Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2))
                * Math.cos(deg2rad(theta));
        dist = Math.acos(dist);
        dist = rad2deg(dist);
        dist = dist * 60 * 1.1515;
        //if (unit == "K") {
        //  dist = dist * 1.609344;
        // else if (unit == "N") {
        //dist = dist * 0.8684;
        //}
        return (dist);
    }


    public static final double PI = 3.14159265;
    public static final double deg2radians = PI/180.0;


    public static double getDistance(double latitude1, double longitude1, double latitude2,double longitude2) {

        double lat1 = latitude1 * deg2radians;
        double lat2 = latitude2 * deg2radians;
        double lon1 = longitude1 * deg2radians;
        double lon2 = longitude2 * deg2radians;
        // Williams gives two formulae;
        // this is the more accurate for close distances.
        // In practice, the two differed only in the 8th or 9th place, for
        // separations as small as 1 degree.
        double radd = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin((lat1 - lat2) / 2),
                2.0)
                + Math.cos(lat1)
                * Math.cos(lat2)
                * Math.pow(Math.sin((lon1 - lon2) / 2), 2.0)));

        return radd;
    }





    /* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
    /* :: This function converts decimal degrees to radians : */
    /* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
    private static double deg2rad(double deg) {
        return (deg * Math.PI / 180.0);
    }

    /* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
    /* :: This function converts radians to decimal degrees : */
    /* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
    private static double rad2deg(double rad) {
        return (rad * 180.0 / Math.PI);
    }

}

double CalculateDistance( double nLat1, double nLon1, double nLat2, double nLon2 )
{
    double nRadius = 6371; // Earth's radius in Kilometers
    // Get the difference between our two points
    // then convert the difference into radians

    double nDLat = ToRad(nLat2 - nLat1);
    double nDLon = ToRad(nLon2 - nLon1);

    // Here is the new line
    nLat1 =  ToRad(nLat1);
    nLat2 =  ToRad(nLat2);

    double nA = pow ( sin(nDLat/2), 2 ) + cos(nLat1) * cos(nLat2) * pow ( sin(nDLon/2), 2 );

    double nC = 2 * atan2( sqrt(nA), sqrt( 1 - nA ));
    double nD = nRadius * nC;

    return nD; // Return our calculated distance
}

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