android - how can I get the bearing degree between two locations?

Question

As title said, I have current location, and want to know the bearing in degree from my current location to other location. I have read this post, is the value return by location.getBearing() my answer?

Let say it simply: from the picture, I expect the value of 45 degree.

Liaoning

What does the documentation for that method tell you? This question is impossible to answers since you have not said why you think this getBearing() is not the right method. – Panjabi

Use float bearing = myLocation.bearingTo(otherLocation); – Wheelwright

Answer 1

I was having trouble doing this and managed to figure it out converting the C? approach to working out the bearing degree.

I worked this out using 4 coordinate points

Start Latitude

Start Longitude

End Latitude

End Longitude

Here's the code:

    protected double bearing(double startLat, double startLng, double endLat, double endLng){
    double latitude1 = Math.toRadians(startLat);
    double latitude2 = Math.toRadians(endLat);
    double longDiff= Math.toRadians(endLng - startLng);
    double y= Math.sin(longDiff)*Math.cos(latitude2);
    double x=Math.cos(latitude1)*Math.sin(latitude2)-Math.sin(latitude1)*Math.cos(latitude2)*Math.cos(longDiff);

    return (Math.toDegrees(Math.atan2(y, x))+360)%360;
}

Just change the variable names were needed.

Output bearing to a TextView

Hope it helped!

Dieldrin

I have tried the same but I am getting a 90 degree offset, I have given same location for start and end which should give me 0 degrees, I also tried a location in 180 degree but same result – Hogan

Answer 2

Location have method bearingTo: float bearingTo(Location dest)

Location from = new Location(LocationManager.GPS_PROVIDER);
Location to = new Location(LocationManager.GPS_PROVIDER);
from.setLatitude(0);
from.setLongitude(0);
to.setLongitude(10);
to.setLatitude(10);

float bearingTo = from.bearingTo(to);

Warfield

This method is giving me 90 degree offset on same location and location having 180 degree bearing – Hogan

Answer 3

Here is the code for calculating bearing angle between two points(startPoint, endPoint):

public float CalculateBearingAngle(double startLatitude,double startLongitude, double endLatitude, double endLongitude){
    double Phi1 = Math.toRadians(startLatitude);
    double Phi2 = Math.toRadians(endLatitude);
    double DeltaLambda = Math.toRadians(endLongitude - startLongitude);

    double Theta = atan2((sin(DeltaLambda)*cos(Phi2)) , (cos(Phi1)*sin(Phi2) - sin(Phi1)*cos(Phi2)*cos(DeltaLambda)));
    return (float)Math.toDegrees(Theta);
}

Call for function:

float angle = CalculateBearingAngle(startLatitude, startLongitude, endLatitude, endLongitude);

Filet

Answer 4

I found best method for calculating "Bearing between two point " from this answer and convert it to java from python. And this method work like charm for me!

here is the code:

    public static double getBearing(double startLat, double startLng, double endLat, double endLng) {

    double latitude1 = Math.toRadians(startLat);
    double longitude1 = Math.toRadians(-startLng);
    double latitude2 = Math.toRadians(endLat);
    double longitude2 = Math.toRadians(-endLng);

    double dLong = longitude2 - longitude1;

    double dPhi = Math.log(Math.tan(latitude2 / 2.0 + Math.PI / 4.0) / Math.tan(latitude1 / 2.0 + Math.PI / 4.0));
    if (abs(dLong) > Math.PI)
        if (dLong > 0.0)
            dLong = -(2.0 * Math.PI - dLong);
        else
            dLong = (2.0 * Math.PI + dLong);

   return  (Math.toDegrees(Math.atan2(dLong, dPhi)) + 360.0) % 360.0;
}

Lebaron