Android Open Source - Toury-Glass Direction Utils

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License

The source code is released under:

MIT License

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Java Source Code

package twilight.of.the.devs.utils;
/*  w w w.  j a  va2s .  c  om*/
import android.location.Location;
import android.util.Log;

/*
 * Utilities for determining the user's direction
 */
public class DirectionUtils {

  public enum DIRECTION {LEFT, RIGHT, BEHIND}

  private static final String TAG = DirectionUtils.class.getName();
  
  /*
   * Determines on which side of the user the current marker is.
   * @param bearingTo the bearing to the marker we want to determine the side of
   * @param currentHeading the user's currentHeading
   */
  public static DIRECTION isOnWhichSide(double bearingTo, double currentHeading){
    double diff = Math.abs(bearingTo - currentHeading);
    if(bearingTo > 270 && currentHeading < 90){
      bearingTo = 360 - bearingTo;
      diff = bearingTo + currentHeading;
    } else if (bearingTo < 90 && currentHeading > 270){
      currentHeading = 360 - currentHeading;
      diff = currentHeading + bearingTo;
    }
    if(diff < 0) diff += 360;
    Log.d(TAG, "Diff " + diff);
    
    //Return left, right, or behind based on the previous calculations
    if(bearingTo < currentHeading && diff < 80) return DIRECTION.LEFT;
    else if (bearingTo > currentHeading && diff < 80) return DIRECTION.RIGHT;
    else return DIRECTION.BEHIND;
  }
  
  /*
   * Converts a negative bearing to positive
   * @param bearing the bearing
   * @return the new (non-negative) bearing
   */
  public static double convertBearing(double bearing){
    if(bearing >= 0) return bearing;
    return bearing + 360;
  }
  
  /* The following code is from the Android Compass Example Code */
  
  /**
     * Calculates {@code a mod b} in a way that respects negative values (for example,
     * {@code mod(-1, 5) == 4}, rather than {@code -1}).
     *
     * @param a the dividend
     * @param b the divisor
     * @return {@code a mod b}
     */
    public static float mod(float a, float b) {
        return (a % b + b) % b;
    }
  
  /**
     * Gets the relative bearing from one geographical coordinate to another.
     *
     * @param latitude1 the latitude of the source point
     * @param longitude1 the longitude of the source point
     * @param latitude2 the latitude of the destination point
     * @param longitude2 the longitude of the destination point
     * @return the relative bearing from point 1 to point 2, in degrees. The result is guaranteed
     *         to fall in the range 0-360
     */
    public static float getBearing(double latitude1, double longitude1, double latitude2,
            double longitude2) {
        latitude1 = Math.toRadians(latitude1);
        longitude1 = Math.toRadians(longitude1);
        latitude2 = Math.toRadians(latitude2);
        longitude2 = Math.toRadians(longitude2);

        double dLon = longitude2 - longitude1;

        double y = Math.sin(dLon) * Math.cos(latitude2);
        double x = Math.cos(latitude1) * Math.sin(latitude2) - Math.sin(latitude1)
                * Math.cos(latitude2) * Math.cos(dLon);

        double bearing = Math.atan2(y, x);
        return mod((float) Math.toDegrees(bearing), 360.0f);
    }
}

Java Source Code List