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Lucene example source code file (DistanceApproximation.java)

This example Lucene source code file (DistanceApproximation.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

deprecated, deprecated, distanceapproximation, distanceapproximation, kilometers_per_mile, kilometers_per_mile, miles_per_latitude, miles_per_latitude

The Lucene DistanceApproximation.java source code

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.lucene.spatial.geometry.shape;

/**
 * Imported from mq java client.  No changes made.
 *
 * <p>NOTE: This API is still in
 * flux and might change in incompatible ways in the next
 * release.</font>
 *
 * @deprecated This has been replaced with more accurate
 * math in {@link LLRect}. This class will be removed in a future release.
 */
@Deprecated
public class DistanceApproximation
{
  private double m_testLat;
  private double m_testLng;
  private double m_mpd;
  private static final double m_milesPerLngDeg[]={
     69.170976f, 69.160441f, 69.128838f, 69.076177f, 69.002475f,
     68.907753f, 68.792041f, 68.655373f, 68.497792f, 68.319345f,
     68.120088f, 67.900079f, 67.659387f, 67.398085f, 67.116253f,
     66.813976f, 66.491346f, 66.148462f, 65.785428f, 65.402355f,
     64.999359f, 64.576564f, 64.134098f, 63.672096f, 63.190698f,
     62.690052f, 62.170310f, 61.631630f, 61.074176f, 60.498118f,
     59.903632f, 59.290899f, 58.660106f, 58.011443f, 57.345111f,
     56.661310f, 55.960250f, 55.242144f, 54.507211f, 53.755675f,
     52.987764f, 52.203713f, 51.403761f, 50.588151f, 49.757131f,
     48.910956f, 48.049882f, 47.174172f, 46.284093f, 45.379915f,
     44.461915f, 43.530372f, 42.585570f, 41.627796f, 40.657342f,
     39.674504f, 38.679582f, 37.672877f, 36.654698f, 35.625354f,
     34.585159f, 33.534429f, 32.473485f, 31.402650f, 30.322249f,
     29.232613f, 28.134073f, 27.026963f, 25.911621f, 24.788387f,
     23.657602f, 22.519612f, 21.374762f, 20.223401f, 19.065881f,
     17.902554f, 16.733774f, 15.559897f, 14.381280f, 13.198283f,
     12.011266f, 10.820591f,  9.626619f,  8.429716f,  7.230245f,
      6.028572f,  4.825062f,  3.620083f,  2.414002f,  1.207185f,
      1.000000f};

  public static final double MILES_PER_LATITUDE   = 69.170976f;
  public static final double KILOMETERS_PER_MILE  = 1.609347f;


  public DistanceApproximation()
  {
  }

  public void setTestPoint(double lat, double lng)
  {
    m_testLat = lat;
    m_testLng = lng;
    m_mpd     = m_milesPerLngDeg[(int)(Math.abs(lat) + 0.5f)];
  }

  // Approximate arc distance between 2 lat,lng positions using miles per
  //    latitude and longitude degree
  public double getDistanceSq(double lat, double lng)
  {
    double latMiles = (lat - m_testLat) * MILES_PER_LATITUDE;

    // Approximate longitude miles using the miles per degree assuming the
    //    middle latitude/longitude.  This is less accurate at high (near
    //    polar) latitudes but no road network is present at the poles!
    //    If we ever have any roads crossing the international date we will
    //    have to worry about that case.
    double lngMiles = (lng - m_testLng) * m_mpd;

     // Find the squared distance by the Pythagorean theorem (without sqrt)
    return (latMiles * latMiles + lngMiles * lngMiles);
  }

  // Approximate arc distance between a segment (with lat,lng endpoints) and
  //    the test position
  public double getDistanceSq(double lat1, double lng1, double lat2, double lng2)
  {
     // Check if lat1,lng1 is closest point.  Construct a vector from point1
     //    to point2 (v1) and another from point 1 to the test point (v2).
     //    If dot product is negative then point 1 is the closest point
     double v1y = lat2 - lat1;
     double v1x = lng2 - lng1;
     double v2y = m_testLat - lat1;
     double v2x = m_testLng - lng1;
     double dot = v1x * v2x + v1y * v2y;
     if (dot <= 0.0f)
        return getDistanceSq(lat1, lng1);

     // Get the component of vector v2 along v1.  If component is greater
     //    than 1 then the endpoint is the closest point.
     double c = dot / (v1x * v1x + v1y * v1y);
     if (c >= 1.0f)
        return getDistanceSq(lat2, lng2);

     // Since we are working io lat,lng space we need to find the point
     //    along p1->p2 such that q->pt is perpendicular to p1->p2.  We
     //    then find the distance squared between Q and pt.
     return getDistanceSq((lat1 + v1y * c), (lng1 + v1x * c));
  }

  // Return the number of miles per degree of longitude
  public static double getMilesPerLngDeg(double lat)
  {
     return (Math.abs(lat) <= 90.0) ? m_milesPerLngDeg[(int)(Math.abs(lat) + 0.5f)] : 69.170976f;
  }
  
  public static double getMilesPerLatDeg() {
    return MILES_PER_LATITUDE;
  }
}

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