NOTE: This API is still in flux and might change in incompatible ways in the next release. + */ +public interface GeoDistanceCalculator { + + /** + * Calculates the distance between the point defined by the source latitude/longitude and the point defined by the + * target latitude/longitude + * + * @param sourceLongitude Longitude of the point the distance is being calculated from + * @param sourceLatitude Latitude of the point the distance is being calculated from + * @param targetLongitude Longitude of the point the distance is being calculated to + * @param targetLatitude Latitude of the point the distance is being calculated to + * @param unit Unit of distance the result should be returned in + * @return Distance between the 2 points in the unit of distance requested + */ + double calculate(double sourceLatitude, double sourceLongitude, double targetLatitude, double targetLongitude, DistanceUnits unit); +} Index: contrib/spatial/src/java/org/apache/lucene/spatial/geometry/PlaneGeoDistanceCalculator.java =================================================================== --- contrib/spatial/src/java/org/apache/lucene/spatial/geometry/PlaneGeoDistanceCalculator.java Fri Dec 11 15:02:01 CET 2009 +++ contrib/spatial/src/java/org/apache/lucene/spatial/geometry/PlaneGeoDistanceCalculator.java Fri Dec 11 15:02:01 CET 2009 @@ -0,0 +1,49 @@ +/** + * 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; + +import org.apache.lucene.spatial.util.SpatialConstants; + +/** + * Implementation of {@link GeoDistanceCalculator} that assumes that the 2 points are on a flat plane. + *
+ * Obviously since the world is curved, this calculation with have some error. However in many cases, the bigger the + * distance, the less important the error. The impact of doing such a simple calculation is that the performance of + * calculating the distance of millions of points is considerably reduced. + * + *NOTE: This API is still in flux and might change in incompatible ways in the next release. + */ +public class PlaneGeoDistanceCalculator implements GeoDistanceCalculator { + + private final static double DISTANCE_PER_DEGREE = SpatialConstants.EARTH_CIRCUMFERENCE_MILES / 360; + + /** + * {@inheritDoc} + */ + public double calculate( + double sourceLatitude, + double sourceLongitude, + double targetLatitude, + double targetLongitude, + DistanceUnits unit) { + double px = targetLongitude - sourceLongitude; + double py = targetLatitude - sourceLatitude; + double distanceMiles = Math.sqrt(px * px + py * py) * DISTANCE_PER_DEGREE; + return DistanceUnits.convert(distanceMiles, DistanceUnits.MILES, unit); + } +} Index: contrib/spatial/src/java/org/apache/lucene/spatial/geometry/ArcGeoDistanceCalculator.java =================================================================== --- contrib/spatial/src/java/org/apache/lucene/spatial/geometry/ArcGeoDistanceCalculator.java Fri Dec 11 15:00:28 CET 2009 +++ contrib/spatial/src/java/org/apache/lucene/spatial/geometry/ArcGeoDistanceCalculator.java Fri Dec 11 15:00:28 CET 2009 @@ -0,0 +1,40 @@ +/** + * 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; + +/** + * Implementation of {@link GeoDistanceCalculator} that calculates distances as though the points are on a globe. + * + *
NOTE: This API is still in flux and might change in incompatible ways in the next release. + */ +public class ArcGeoDistanceCalculator implements GeoDistanceCalculator { + + /** + * {@inheritDoc} + */ + public double calculate( + double sourceLatitude, + double sourceLongitude, + double targetLatitude, + double targetLongitude, + DistanceUnits unit) { + LatLng sourcePoint = new LatLng(sourceLatitude, sourceLongitude); + LatLng targetPoint = new LatLng(targetLatitude, targetLongitude); + return DistanceUnits.convert(sourcePoint.arcDistance(targetPoint, DistanceUnits.MILES), DistanceUnits.MILES, unit); + } +} Index: contrib/spatial/src/test/org/apache/lucene/spatial/geometry/TestPlaneGeoDistanceCalculator.java =================================================================== --- contrib/spatial/src/test/org/apache/lucene/spatial/geometry/TestPlaneGeoDistanceCalculator.java Fri Dec 11 15:04:57 CET 2009 +++ contrib/spatial/src/test/org/apache/lucene/spatial/geometry/TestPlaneGeoDistanceCalculator.java Fri Dec 11 15:04:57 CET 2009 @@ -0,0 +1,42 @@ +/** + * 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; + +import junit.framework.TestCase; + +/** + * Tests for {@link org.apache.lucene.spatial.geometry.PlaneGeoDistanceCalculator} + */ +public class TestPlaneGeoDistanceCalculator extends TestCase { + + /** + * Pass condition: The distance calculated in miles matches the expected distance + */ + public void testCalculate_miles() { + double distance = new PlaneGeoDistanceCalculator().calculate(53.85, 4.51, 43.22, 9.68, DistanceUnits.MILES); + assertEquals(817.6548750234183, distance, 0D); + } + + /** + * Pass condition: The distance calculated in kilometers matches the expected distance + */ + public void testCalculate_kilometers() { + double distance = new PlaneGeoDistanceCalculator().calculate(53.85, 4.51, 43.22, 9.68, DistanceUnits.KILOMETERS); + assertEquals(1315.8879671896882, distance, 0D); + } +}