问题
I have calculated angle between two Latitude and Longitude coordinates as below code.It returns angle as 3 in radians, and 193 in degrees. I want to show arrow marker on map based on this angle.How to display object direction moved,based on this angle?
public static double getAngle(double lat1, double lon1, double lat2, double lon2)
{
//Formulas
//θ = atan2( sin(Δlong).cos(lat2),cos(lat1).sin(lat2) − sin(lat1).cos(lat2).cos(Δlong) )
// Δlong = long2 - long1
Log.i("angle", "Inside getAngle");
double latitude1 = Math.toRadians(lat1);
double longitude1 = Math.toRadians(lon1);
double latitude2 = Math.toRadians(lat2);
double longitude2 = Math.toRadians(lon2);
double dlong = Math.toRadians(longitude2-longitude1);
double y = Math.sin(dlong) * Math.cos(latitude2);
double x = Math.cos(latitude1)*Math.sin(latitude2) - Math.sin(latitude1)*Math.cos(latitude2)*Math.cos(dlong);
double angle= Math.atan2(y, x);
if (angle < 0)
angle = Math.abs(angle);
else
angle = 2*Math.PI - angle;
Log.i("angle", String.valueOf(angle)+" in radians");
angle=Math.toDegrees(angle);
Log.i("angle", String.valueOf(angle)+" in degrees");
return angle;
}
回答1:
I got angle and rotate arrow image on same angle on Map.This makes like direction of Route.
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
/* inside for loop of all Latitude Longitude values */
float angle=(float)finalBearing(previousLocationLatitude, previousLocationLongitude, currentLocationLatitude, currentLocationLongitude);
Bitmap sprite = BitmapFactory.decodeResource(this.getResources(),R.drawable.dir_green_image);
Matrix mat = new Matrix();
mat.preRotate(angle);///in degree
Bitmap mBitmap = Bitmap.createBitmap(sprite, 0, 0, sprite.getWidth(), sprite.getHeight(), mat, true);
mMap.addMarker(new MarkerOptions().position(new LatLng(currentLocationLatitude, currentLocationLongitude)).icon(BitmapDescriptorFactory.fromBitmap(mBitmap)).anchor((float)0.5, (float)0.5));
/* inside for loop of all Latitude Longitude values */
static public double initialBearing (double lat1, double long1, double lat2, double long2)
{
return (_bearing(lat1, long1, lat2, long2) + 360.0) % 360;
}
static public double finalBearing(double lat1, double long1, double lat2, double long2)
{
return (_bearing(lat2, long2, lat1, long1) + 180.0) % 360;
}
static private double _bearing(double lat1, double long1, double lat2, double long2)
{
double degToRad = Math.PI / 180.0;
double phi1 = lat1 * degToRad;
double phi2 = lat2 * degToRad;
double lam1 = long1 * degToRad;
double lam2 = long2 * degToRad;
return Math.atan2(Math.sin(lam2-lam1)*Math.cos(phi2),
Math.cos(phi1)*Math.sin(phi2) - Math.sin(phi1)*Math.cos(phi2)*Math.cos(lam2-lam1)
) * 180/Math.PI;
}
来源:https://stackoverflow.com/questions/15745002/how-to-show-direction-on-map-based-on-calculated-angle-in-degrees