GeoDistanceTests.java

/*
 * Licensed to ElasticSearch and Shay Banon under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. ElasticSearch 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
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package org.elasticsearch.test.unit.index.search.geo;

import org.elasticsearch.common.unit.DistanceUnit;
import org.elasticsearch.index.search.geo.GeoDistance;
import org.elasticsearch.index.search.geo.Point;
import org.testng.annotations.Test;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.greaterThan;
import static org.hamcrest.Matchers.lessThan;

/**
 */
@Test
public class GeoDistanceTests {

    @Test
    public void testDistanceCheck() {
        // Note, is within is an approximation, so, even though 0.52 is outside 50mi, we still get "true"
        GeoDistance.DistanceBoundingCheck check = GeoDistance.distanceBoundingCheck(0, 0, 50, DistanceUnit.MILES);
        assertThat(check.isWithin(0.5, 0.5), equalTo(true));
        assertThat(check.isWithin(0.52, 0.52), equalTo(true));
        assertThat(check.isWithin(1, 1), equalTo(false));

        check = GeoDistance.distanceBoundingCheck(0, 179, 200, DistanceUnit.MILES);
        assertThat(check.isWithin(0, -179), equalTo(true));
        assertThat(check.isWithin(0, -178), equalTo(false));
    }

    @Test
    public void testArcDistanceVsPlaneInEllipsis() {
        Point centre = new Point(48.8534100, 2.3488000);
        Point northernPoint = new Point(48.8801108681, 2.35152032666);
        Point westernPoint = new Point(48.85265, 2.308896);

        // With GeoDistance.ARC both the northern and western points are within the 4km range
        assertThat(GeoDistance.ARC.calculate(centre.lat, centre.lon, northernPoint.lat,
                northernPoint.lon, DistanceUnit.KILOMETERS), lessThan(4D));
        assertThat(GeoDistance.ARC.calculate(centre.lat, centre.lon, westernPoint.lat,
                westernPoint.lon, DistanceUnit.KILOMETERS), lessThan(4D));

        // With GeoDistance.PLANE, only the northern point is within the 4km range,
        // the western point is outside of the range due to the simple math it employs,
        // meaning results will appear elliptical
        assertThat(GeoDistance.PLANE.calculate(centre.lat, centre.lon, northernPoint.lat,
                northernPoint.lon, DistanceUnit.KILOMETERS), lessThan(4D));
        assertThat(GeoDistance.PLANE.calculate(centre.lat, centre.lon, westernPoint.lat,
                westernPoint.lon, DistanceUnit.KILOMETERS), greaterThan(4D));
    }
}