TravelToolsUtils.java

public final class TravelToolsUtils {
    /**
     * Generate mock stop locations, given current location of user.
     */
    public static CoordinatesEntity getCoordinatesEntity(double x0, double y0, double radius) {
        Random random = new Random();

        // Convert radius from meters to degrees
        double w = (radius / 111000f) * Math.sqrt(random.nextDouble());
        double t = 2 * Math.PI * random.nextDouble();
        double x = w * Math.cos(t);
        double y = w * Math.sin(t);

        // Adjust the x-coordinate for the shrinking of the east-west distances
        double new_x = x / Math.cos(y0);

        double foundLongitude = new_x + x0;
        double foundLatitude = y + y0;

        return CoordinatesEntity.create(String.valueOf(foundLatitude),
                                        String.valueOf(foundLongitude));
    }
  
   /**
     * Given LatLngBounds, get the radius.
     */
   public static double getBoundsRadius(@NonNull LatLngBounds bounds) {
        LatLng center = bounds.getCenter();
        LatLng ne = bounds.northeast;
        double degreesToRadians = 57.2958;
     
        double ne_lat = ne.latitude / degreesToRadians;
        double ne_lng = ne.longitude / degreesToRadians;
        double c_lat = center.latitude / degreesToRadians;
        double c_lng = center.longitude / degreesToRadians;

        // distance = circle radius from center to Northeast corner of bounds
        double r_km = 6378.8 * Math.acos(
                Math.sin(c_lat) * Math.sin(ne_lat) +
                Math.cos(c_lat) * Math.cos(ne_lat) * Math.cos(ne_lng - c_lng));
        return r_km * 1000;
    }
}