* setup accurate GeoDistance Function

* adapt tests
* introduced default GeoDistance function
* Updated docs

closes #4498

docs/reference/query-dsl/filters/geo-distance-filter.asciidoc

@@ -148,8 +148,9 @@ The following are options allowed on the filter:
 
 `distance_type`::
 
-    How to compute the distance. Can either be `arc` (better precision) or
-    `plane` (faster). Defaults to `arc`.
+    How to compute the distance. Can either be `arc` (better precision),
+    `sloppy_arc` (faster but less precise) or `plane` (fastest). Defaults
+    to `sloppy_arc`.
 
 `optimize_bbox`::
 

docs/reference/search/aggregations/bucket/geodistance-aggregation.asciidoc

@@ -80,7 +80,7 @@ By default, the distance unit is `km` but it can also accept: `mi` (miles), `in`
 
 <1> The distances will be computed as miles
 
-There are two distance calculation modes: `arc` (the default) and `plane`. The `arc` calculation is the most accurate one but also the more expensive one in terms of performance. The `plane` is faster but less accurate. Consider using `plane` when your search context is "narrow" and spans smaller geographical areas (like cities or even countries). `plane` may return higher error mergins for searches across very large areas (e.g. cross continent search). The distance calculation type can be set using the `distance_type` parameter:
+There are two distance calculation modes: `sloppy_arc` (the default), `arc` (most accurate) and `plane` (fastest). The `arc` calculation is the most accurate one but also the more expensive one in terms of performance. The `sloppy_arc` is faster but less accurate. The `plane` is the fastest but least accurate distance function. Consider using `plane` when your search context is "narrow" and spans smaller geographical areas (like cities or even countries). `plane` may return higher error mergins for searches across very large areas (e.g. cross continent search). The distance calculation type can be set using the `distance_type` parameter:
 
 [source,js]
 --------------------------------------------------

docs/reference/search/facets/geo-distance-facet.asciidoc

@@ -172,7 +172,7 @@ itself.
 be `mi`, `miles`, `in`, `inch`, `yd`, `yards`, `kilometers`, `mm`, `millimeters`, `cm`, `centimeters`, `m` or `meters`.
 
 |`distance_type` |How to compute the distance. Can either be `arc`
-(better precision) or `plane` (faster). Defaults to `arc`.
+(better precision), `sloppy_arc` (faster) or `plane` (fastest). Defaults to `sloppy_arc`.
 |=======================================================================
 
 ==== Value Options

src/main/java/org/elasticsearch/common/geo/GeoDistance.java

@@ -23,6 +23,8 @@
 import org.elasticsearch.ElasticSearchIllegalArgumentException;
 import org.elasticsearch.common.unit.DistanceUnit;
 
+import java.util.Locale;
+
 /**
  * Geo distance calculation.
  */
@@ -48,6 +50,7 @@ public FixedSourceDistance fixedSourceDistance(double sourceLatitude, double sou
             return new PlaneFixedSourceDistance(sourceLatitude, sourceLongitude, unit);
         }
     },
+
     /**
      * Calculates distance factor.
      */
@@ -71,12 +74,23 @@ public FixedSourceDistance fixedSourceDistance(double sourceLatitude, double sou
         }
     },
     /**
-     * Calculates distance as points in a globe.
+     * Calculates distance as points on a globe.
      */
     ARC() {
         @Override
         public double calculate(double sourceLatitude, double sourceLongitude, double targetLatitude, double targetLongitude, DistanceUnit unit) {
-            return unit.fromMeters(SloppyMath.haversin(sourceLatitude, sourceLongitude, targetLatitude, targetLongitude) * 1000.0);
+            double longitudeDifference = targetLongitude - sourceLongitude;
+            double a = Math.toRadians(90D - sourceLatitude);
+            double c = Math.toRadians(90D - targetLatitude);
+            double factor = (Math.cos(a) * Math.cos(c)) + (Math.sin(a) * Math.sin(c) * Math.cos(Math.toRadians(longitudeDifference)));
+
+            if (factor < -1D) {
+                return unit.fromMeters(Math.PI * GeoUtils.EARTH_MEAN_RADIUS);
+            } else if (factor >= 1D) {
+                return 0;
+            } else {
+                return unit.fromMeters(Math.acos(factor) * GeoUtils.EARTH_MEAN_RADIUS);
+            }
         }
 
         @Override
@@ -88,8 +102,35 @@ public double normalize(double distance, DistanceUnit unit) {
         public FixedSourceDistance fixedSourceDistance(double sourceLatitude, double sourceLongitude, DistanceUnit unit) {
             return new ArcFixedSourceDistance(sourceLatitude, sourceLongitude, unit);
         }
+    },
+    /**
+     * Calculates distance as points on a globe in a sloppy way. Close to the pole areas the accuracy
+     * of this function decreases.
+     */
+    SLOPPY_ARC() {
+
+        @Override
+        public double normalize(double distance, DistanceUnit unit) {
+            return distance;
+        }
+
+        @Override
+        public double calculate(double sourceLatitude, double sourceLongitude, double targetLatitude, double targetLongitude, DistanceUnit unit) {
+            return unit.fromMeters(SloppyMath.haversin(sourceLatitude, sourceLongitude, targetLatitude, targetLongitude) * 1000.0);
+        }
+
+        @Override
+        public FixedSourceDistance fixedSourceDistance(double sourceLatitude, double sourceLongitude, DistanceUnit unit) {
+            return new SloppyArcFixedSourceDistance(sourceLatitude, sourceLongitude, unit);
+        }
     };
 
+    /**
+     * Default {@link GeoDistance} function. This method should be used, If no specific function has been selected.
+     * This is an alias for <code>SLOPPY_ARC</code>
+     */
+    public static final GeoDistance DEFAULT = SLOPPY_ARC; 
+
     public abstract double normalize(double distance, DistanceUnit unit);
 
     public abstract double calculate(double sourceLatitude, double sourceLongitude, double targetLatitude, double targetLongitude, DistanceUnit unit);
@@ -134,15 +175,31 @@ public static DistanceBoundingCheck distanceBoundingCheck(double sourceLatitude,
         return new SimpleDistanceBoundingCheck(topLeft, bottomRight);
     }
 
-    public static GeoDistance fromString(String s) {
-        if ("plane".equals(s)) {
+    /**
+     * Get a {@link GeoDistance} according to a given name. Valid values are
+     * 
+     * <ul>
+     *     <li><b>plane</b> for <code>GeoDistance.PLANE</code></li>
+     *     <li><b>sloppy_arc</b> for <code>GeoDistance.SLOPPY_ARC</code></li>
+     *     <li><b>factor</b> for <code>GeoDistance.FACTOR</code></li>
+     *     <li><b>arc</b> for <code>GeoDistance.ARC</code></li>
+     * </ul>
+     * 
+     * @param name name of the {@link GeoDistance}
+     * @return a {@link GeoDistance}
+     */
+    public static GeoDistance fromString(String name) {
+        name = name.toLowerCase(Locale.ROOT);
+        if ("plane".equals(name)) {
             return PLANE;
-        } else if ("arc".equals(s)) {
+        } else if ("arc".equals(name)) {
             return ARC;
-        } else if ("factor".equals(s)) {
+        } else if ("sloppy_arc".equals(name)) {
+            return SLOPPY_ARC;
+        } else if ("factor".equals(name)) {
             return FACTOR;
         }
-        throw new ElasticSearchIllegalArgumentException("No geo distance for [" + s + "]");
+        throw new ElasticSearchIllegalArgumentException("No geo distance for [" + name + "]");
     }
 
     public static interface FixedSourceDistance {
@@ -253,18 +310,14 @@ public double calculate(double targetLatitude, double targetLongitude) {
 
     public static class FactorFixedSourceDistance implements FixedSourceDistance {
 
-        private final double sourceLatitude;
         private final double sourceLongitude;
-        private final double earthRadius;
 
         private final double a;
         private final double sinA;
         private final double cosA;
 
         public FactorFixedSourceDistance(double sourceLatitude, double sourceLongitude, DistanceUnit unit) {
-            this.sourceLatitude = sourceLatitude;
             this.sourceLongitude = sourceLongitude;
-            this.earthRadius = unit.getEarthRadius();
             this.a = Math.toRadians(90D - sourceLatitude);
             this.sinA = Math.sin(a);
             this.cosA = Math.cos(a);
@@ -278,21 +331,44 @@ public double calculate(double targetLatitude, double targetLongitude) {
         }
     }
 
-    public static class ArcFixedSourceDistance implements FixedSourceDistance {
-
-        private final double sourceLatitude;
-        private final double sourceLongitude;
-        private final DistanceUnit unit;
+    /**
+     * Basic implementation of {@link FixedSourceDistance}. This class keeps the basic parameters for a distance
+     * functions based on a fixed source. Namely latitude, longitude and unit. 
+     */
+    public static abstract class FixedSourceDistanceBase implements FixedSourceDistance {
+        protected final double sourceLatitude;
+        protected final double sourceLongitude;
+        protected final DistanceUnit unit;
 
-        public ArcFixedSourceDistance(double sourceLatitude, double sourceLongitude, DistanceUnit unit) {
+        public FixedSourceDistanceBase(double sourceLatitude, double sourceLongitude, DistanceUnit unit) {
             this.sourceLatitude = sourceLatitude;
             this.sourceLongitude = sourceLongitude;
             this.unit = unit;
         }
+    }
+
+    public static class ArcFixedSourceDistance extends FixedSourceDistanceBase {
+
+        public ArcFixedSourceDistance(double sourceLatitude, double sourceLongitude, DistanceUnit unit) {
+            super(sourceLatitude, sourceLongitude, unit);
+        }
 
         @Override
         public double calculate(double targetLatitude, double targetLongitude) {
-            return unit.fromMeters(SloppyMath.haversin(sourceLatitude, sourceLongitude, targetLatitude, targetLongitude) * 1000.0);
+            return ARC.calculate(sourceLatitude, sourceLongitude, targetLatitude, targetLongitude, unit);
+        }
+
+    }
+
+    public static class SloppyArcFixedSourceDistance extends FixedSourceDistanceBase {
+
+        public SloppyArcFixedSourceDistance(double sourceLatitude, double sourceLongitude, DistanceUnit unit) {
+            super(sourceLatitude, sourceLongitude, unit);
+        }
+
+        @Override
+        public double calculate(double targetLatitude, double targetLongitude) {
+            return SLOPPY_ARC.calculate(sourceLatitude, sourceLongitude, targetLatitude, targetLongitude, unit);
         }
     }
 }

src/main/java/org/elasticsearch/index/query/GeoDistanceFilterParser.java

@@ -74,7 +74,7 @@ public Filter parse(QueryParseContext parseContext) throws IOException, QueryPar
         double distance = 0;
         Object vDistance = null;
         DistanceUnit unit = DistanceUnit.KILOMETERS; // default unit
-        GeoDistance geoDistance = GeoDistance.ARC;
+        GeoDistance geoDistance = GeoDistance.DEFAULT;
         String optimizeBbox = "memory";
         boolean normalizeLon = true;
         boolean normalizeLat = true;

src/main/java/org/elasticsearch/index/query/GeoDistanceRangeFilterParser.java

@@ -76,7 +76,7 @@ public Filter parse(QueryParseContext parseContext) throws IOException, QueryPar
         boolean includeLower = true;
         boolean includeUpper = true;
         DistanceUnit unit = DistanceUnit.KILOMETERS; // default unit
-        GeoDistance geoDistance = GeoDistance.ARC;
+        GeoDistance geoDistance = GeoDistance.DEFAULT;
         String optimizeBbox = "memory";
         boolean normalizeLon = true;
         boolean normalizeLat = true;

src/main/java/org/elasticsearch/index/query/functionscore/DecayFunctionParser.java

@@ -270,7 +270,7 @@ static class GeoFieldDataScoreFunction extends AbstractDistanceScoreFunction {
         private final IndexGeoPointFieldData<?> fieldData;
         private GeoPointValues geoPointValues = null;
 
-        private static final GeoDistance distFunction = GeoDistance.fromString("arc");
+        private static final GeoDistance distFunction = GeoDistance.DEFAULT;
 
         public GeoFieldDataScoreFunction(GeoPoint origin, double scale, double decay, double offset, DecayFunction func,
                 IndexGeoPointFieldData<?> fieldData) {

src/main/java/org/elasticsearch/search/aggregations/bucket/range/geodistance/GeoDistanceParser.java

@@ -68,7 +68,7 @@ public AggregatorFactory parse(String aggregationName, XContentParser parser, Se
         List<RangeAggregator.Range> ranges = null;
         GeoPoint origin = null;
         DistanceUnit unit = DistanceUnit.KILOMETERS;
-        GeoDistance distanceType = GeoDistance.ARC;
+        GeoDistance distanceType = GeoDistance.DEFAULT;
         boolean keyed = false;
 
         XContentParser.Token token;

src/main/java/org/elasticsearch/search/facet/geodistance/GeoDistanceFacetParser.java

@@ -22,7 +22,6 @@
 import com.google.common.collect.Lists;
 import org.elasticsearch.common.component.AbstractComponent;
 import org.elasticsearch.common.geo.GeoDistance;
-import org.elasticsearch.common.geo.GeoHashUtils;
 import org.elasticsearch.common.geo.GeoPoint;
 import org.elasticsearch.common.geo.GeoUtils;
 import org.elasticsearch.common.inject.Inject;
@@ -32,7 +31,6 @@
 import org.elasticsearch.index.fielddata.IndexGeoPointFieldData;
 import org.elasticsearch.index.fielddata.IndexNumericFieldData;
 import org.elasticsearch.index.mapper.FieldMapper;
-import org.elasticsearch.index.mapper.geo.GeoPointFieldMapper;
 import org.elasticsearch.search.facet.FacetExecutor;
 import org.elasticsearch.search.facet.FacetParser;
 import org.elasticsearch.search.facet.FacetPhaseExecutionException;
@@ -77,7 +75,7 @@ public FacetExecutor parse(String facetName, XContentParser parser, SearchContex
         Map<String, Object> params = null;
         GeoPoint point = new GeoPoint();
         DistanceUnit unit = DistanceUnit.KILOMETERS;
-        GeoDistance geoDistance = GeoDistance.ARC;
+        GeoDistance geoDistance = GeoDistance.DEFAULT;
         List<GeoDistanceFacet.Entry> entries = Lists.newArrayList();
 
         boolean normalizeLon = true;

src/main/java/org/elasticsearch/search/sort/GeoDistanceSortParser.java

@@ -54,7 +54,7 @@ public SortField parse(XContentParser parser, SearchContext context) throws Exce
         String fieldName = null;
         GeoPoint point = new GeoPoint();
         DistanceUnit unit = DistanceUnit.KILOMETERS;
-        GeoDistance geoDistance = GeoDistance.ARC;
+        GeoDistance geoDistance = GeoDistance.DEFAULT;
         boolean reverse = false;
         SortMode sortMode = null;
         String nestedPath = null;

src/test/java/org/apache/lucene/util/SloppyMathTests.java

@@ -20,18 +20,17 @@
 package org.apache.lucene.util;
 
 import org.elasticsearch.common.geo.GeoDistance;
-import org.elasticsearch.common.geo.GeoUtils;
 import org.elasticsearch.common.unit.DistanceUnit;
 import org.elasticsearch.test.ElasticsearchTestCase;
 import org.junit.Test;
 
 import static org.hamcrest.number.IsCloseTo.closeTo;
 
-public class SloppyMathTests extends ElasticsearchTestCase {
+public class SloppyMathTests extends ElasticsearchTestCase {    
 
     @Test
     public void testAccuracy() {
-        for (double lat1 = -90; lat1 <= 90; lat1+=1) {
+        for (double lat1 = -89; lat1 <= 89; lat1+=1) {
             final double lon1 = randomLongitude();
 
             for (double i = -180; i <= 180; i+=1) {
@@ -45,12 +44,12 @@ public void testAccuracy() {
 
     @Test
     public void testSloppyMath() {
-        assertThat(GeoDistance.ARC.calculate(-46.645, -171.057, -46.644, -171.058, DistanceUnit.METERS), closeTo(134.87709, maxError(134.87709)));
-        assertThat(GeoDistance.ARC.calculate(-77.912, -81.173, -77.912, -81.171, DistanceUnit.METERS), closeTo(46.57161, maxError(46.57161)));
-        assertThat(GeoDistance.ARC.calculate(65.75, -20.708, 65.75, -20.709, DistanceUnit.METERS), closeTo(45.66996, maxError(45.66996)));
-        assertThat(GeoDistance.ARC.calculate(-86.9, 53.738, -86.9, 53.741, DistanceUnit.METERS), closeTo(18.03998, maxError(18.03998)));
-        assertThat(GeoDistance.ARC.calculate(89.041, 115.93, 89.04, 115.946, DistanceUnit.METERS), closeTo(115.11711, maxError(115.11711)));
-        
+        assertThat(GeoDistance.SLOPPY_ARC.calculate(-46.645, -171.057, -46.644, -171.058, DistanceUnit.METERS), closeTo(134.87709, maxError(134.87709)));
+        assertThat(GeoDistance.SLOPPY_ARC.calculate(-77.912, -81.173, -77.912, -81.171, DistanceUnit.METERS), closeTo(46.57161, maxError(46.57161)));
+        assertThat(GeoDistance.SLOPPY_ARC.calculate(65.75, -20.708, 65.75, -20.709, DistanceUnit.METERS), closeTo(45.66996, maxError(45.66996)));
+        assertThat(GeoDistance.SLOPPY_ARC.calculate(-86.9, 53.738, -86.9, 53.741, DistanceUnit.METERS), closeTo(18.03998, maxError(18.03998)));
+        assertThat(GeoDistance.SLOPPY_ARC.calculate(89.041, 115.93, 89.04, 115.946, DistanceUnit.METERS), closeTo(115.11711, maxError(115.11711)));
+
         testSloppyMath(DistanceUnit.METERS, 0.01, 5, 45, 90);
         testSloppyMath(DistanceUnit.KILOMETERS, 0.01, 5, 45, 90);
         testSloppyMath(DistanceUnit.INCH, 0.01, 5, 45, 90);
@@ -66,50 +65,34 @@ private void testSloppyMath(DistanceUnit unit, double...deltaDeg) {
         final double lon1 = randomLongitude();
         logger.info("testing SloppyMath with {} at \"{}, {}\"", unit, lat1, lon1);
 
-        GeoDistance.ArcFixedSourceDistance src = new GeoDistance.ArcFixedSourceDistance(lat1, lon1, unit); 
-
         for (int test = 0; test < deltaDeg.length; test++) {
             for (int i = 0; i < 100; i++) {
+                // crop pole areas, sine we now there the function
+                // is not accurate around lat(89°, 90°) and lat(-90°, -89°)
+                final double lat2 = Math.max(-89.0, Math.min(+89.0, lat1 + (randomDouble() - 0.5) * 2 * deltaDeg[test]));
                 final double lon2 = lon1 + (randomDouble() - 0.5) * 2 * deltaDeg[test];
-                final double lat2 = lat1 + (randomDouble() - 0.5) * 2 * deltaDeg[test];
-
-                final double accurate = unit.fromMeters(accurateHaversin(lat1, lon1, lat2, lon2));
-                final double dist1 = GeoDistance.ARC.calculate(lat1, lon1, lat2, lon2, unit);
-                final double dist2 = src.calculate(lat2, lon2);
+
+                final double accurate = GeoDistance.ARC.calculate(lat1, lon1, lat2, lon2, unit);
+                final double dist = GeoDistance.SLOPPY_ARC.calculate(lat1, lon1, lat2, lon2, unit);
 
-                assertThat("distance between("+lat1+", "+lon1+") and ("+lat2+", "+lon2+"))", dist1, closeTo(accurate, maxError(accurate)));
-                assertThat("distance between("+lat1+", "+lon1+") and ("+lat2+", "+lon2+"))", dist2, closeTo(accurate, maxError(accurate)));
+                assertThat("distance between("+lat1+", "+lon1+") and ("+lat2+", "+lon2+"))", dist, closeTo(accurate, maxError(accurate)));
             }
         }
     }
-
-    // Slow but accurate implementation of the haversin function
-    private static double accurateHaversin(double lat1, double lon1, double lat2, double lon2) {
-        double longitudeDifference = lon2 - lon1;
-        double a = Math.toRadians(90D - lat1);
-        double c = Math.toRadians(90D - lat2);
-        double factor = (Math.cos(a) * Math.cos(c)) + (Math.sin(a) * Math.sin(c) * Math.cos(Math.toRadians(longitudeDifference)));
-
-        if (factor < -1D) {
-            return Math.PI * GeoUtils.EARTH_MEAN_RADIUS;
-        } else if (factor >= 1D) {
-            return 0;
-        } else {
-            return Math.acos(factor) * GeoUtils.EARTH_MEAN_RADIUS;
-        }
-    }
-
+
     private static void assertAccurate(double lat1, double lon1, double lat2, double lon2) {
-        double accurate = accurateHaversin(lat1, lon1, lat2, lon2);
-        double sloppy = GeoDistance.ARC.calculate(lat1, lon1, lat2, lon2, DistanceUnit.METERS);
+        double accurate = GeoDistance.ARC.calculate(lat1, lon1, lat2, lon2, DistanceUnit.METERS);
+        double sloppy = GeoDistance.SLOPPY_ARC.calculate(lat1, lon1, lat2, lon2, DistanceUnit.METERS);
         assertThat("distance between("+lat1+", "+lon1+") and ("+lat2+", "+lon2+"))", sloppy, closeTo(accurate, maxError(accurate)));
     }
 
     private static final double randomLatitude() {
-        return (getRandom().nextDouble() - 0.5) * 180d;
+        // crop pole areas, sine we now there the function
+        // is not accurate around lat(89°, 90°) and lat(-90°, -89°)
+        return (getRandom().nextDouble() - 0.5) * 178.0;
     }
 
     private static final double randomLongitude() {
-        return (getRandom().nextDouble() - 0.5) * 360d;
+        return (getRandom().nextDouble() - 0.5) * 360.0;
     }
 }