LatLong.java

// Copyright 2008 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.android.stardroid.units;

import com.google.android.stardroid.util.Geometry;
import com.google.android.stardroid.util.MathUtil;

/**
 * A simple struct for latitude and longitude.
 * 
 */
public class LatLong {
  public float latitude;
  public float longitude;

  public LatLong(float latitude, float longitude) {
    this.latitude = latitude;
    this.longitude = longitude;
  }

  /**
   * This constructor automatically downcasts the latitude and longitude to
   * floats, so that the previous constructor can be used. It is added as a
   * convenience method, since many of the GPS methods return doubles.
   */
  public LatLong(double latitude, double longitude) {
    this((float)latitude, (float) longitude);
  }

  /**
   * Angular distance between the two points.
   * @param other
   * @return degrees
   */
  public float distanceFrom(LatLong other) {
    // Some misuse of the astronomy math classes
    GeocentricCoordinates otherPnt = GeocentricCoordinates.getInstance(other.longitude,
                                                                       other.latitude);
    GeocentricCoordinates thisPnt = GeocentricCoordinates.getInstance(this.longitude,
                                                                      this.latitude);
    float cosTheta = Geometry.cosineSimilarity(thisPnt, otherPnt);
    return MathUtil.acos(cosTheta) * 180f / MathUtil.PI;
  }
}