Android Open Source - GeoTagger Geo Utils

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Back to project page GeoTagger.

License

The source code is released under:

GNU General Public License

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Java Source Code

package horizon.geotagger;
/*from   w ww  . java2  s . c  om*/
/**
 * Nicked from http://www.johndcook.com/blog/2009/04/27/converting-miles-to-degrees-longitude-or-latitude/
 */
public class GeoUtils
{
  private static final double EARTH_RADIUS_IN_MILES = 3960.0;
  
  private static final double EARTH_RADIUS_IN_KM = 6371.0;
  
  private static final double METER_IN_MILES = 0.000621371192D;
  
  private static final double DEGREES_TO_RADIANS = Math.PI / 180.0;
  
  private static final double RADIANS_TO_DEGREES = 180.0 / Math.PI;
  
  /*

  # Distances are measured in miles.
  # Longitudes and latitudes are measured in degrees.
  # Earth is assumed to be perfectly spherical.

  earth_radius = 3960.0
  degrees_to_radians = math.pi/180.0
  radians_to_degrees = 180.0/math.pi
  
  */

  /**
   * "Given a distance north, return the change in latitude."
   */
  public static double changeInLatitude(double meters)
  {
    double miles = meters * METER_IN_MILES;
    return (miles / EARTH_RADIUS_IN_MILES) * RADIANS_TO_DEGREES;
  }
  
  /**
   * "Given a latitude and a distance west, return the change in longitude."
   */
  public static double changeInLongitude(double latitude, double meters)
  {
    //  Find the radius of a circle around the earth at given latitude.
      double radius  = EARTH_RADIUS_IN_MILES * Math.cos(latitude * DEGREES_TO_RADIANS);
      double miles = meters * METER_IN_MILES;
      return (miles / radius) * RADIANS_TO_DEGREES;
  }    
  
  public static double distance(double latA, double lonA, double latB, double lonB)
  {
    double lat1 = Math.toRadians(latA);
    double lon1 = Math.toRadians(lonA);
    double lat2 = Math.toRadians(latB);
    double lon2 = Math.toRadians(lonB);
    double km = Math.acos(Math.sin(lat1) * Math.sin(lat2) 
        + Math.cos(lat1) * Math.cos(lat2) 
        * Math.cos(lon2-lon1)) * EARTH_RADIUS_IN_KM;
    return km * 1000;
  }
}

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