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55c4a365d7
The returned step was in some case not enough towards normal
coordinates (for example when our search position was was already near the
margin of the central area, and we had to match, using the east or west
neighbor, a very far point). Example:
geoadd points 67.575457940146066 -62.001317572780565 far
geoadd points 66.685439060295664 -58.925040587282297 center
georadius points 66.685439060295664 -58.925040587282297 200 km
In the above case the code failed to find a match (happens at smaller
latitudes too) even if far and center are at less than 200km.
Another fix introduced by this commit is a progressively larger area
towards the poles, since meridians are a lot less far away, so we need
to compensate for this.
The current implementation works comparably to the Tcl brute-force
stress tester implemented in the fuzzy test in the geo.tcl unit for
latitudes between -70 and 70, and is pretty accurate over +/-80 too,
with sporadic false negatives.
A more mathematically clean implementation is possible by computing the
meridian distance at the specified latitude and computing the step
according to it.
78 lines
3.6 KiB
C
78 lines
3.6 KiB
C
/*
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* Copyright (c) 2013-2014, yinqiwen <yinqiwen@gmail.com>
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* Copyright (c) 2014, Matt Stancliff <matt@genges.com>.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of Redis nor the names of its contributors may be used
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* to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef GEOHASH_HELPER_HPP_
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#define GEOHASH_HELPER_HPP_
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#include <math.h>
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#include "geohash.h"
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#define GZERO(s) s.bits = s.step = 0;
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#define GISZERO(s) (!s.bits && !s.step)
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#define GISNOTZERO(s) (s.bits || s.step)
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typedef uint64_t GeoHashFix52Bits;
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typedef uint64_t GeoHashVarBits;
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typedef struct {
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GeoHashBits hash;
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GeoHashArea area;
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GeoHashNeighbors neighbors;
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} GeoHashRadius;
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int GeoHashBitsComparator(const GeoHashBits *a, const GeoHashBits *b);
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uint8_t geohashEstimateStepsByRadius(double range_meters, double lat);
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int geohashBoundingBox(double latitude, double longitude, double radius_meters,
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double *bounds);
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GeoHashRadius geohashGetAreasByRadius(double latitude,
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double longitude, double radius_meters);
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GeoHashRadius geohashGetAreasByRadiusWGS84(double latitude, double longitude,
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double radius_meters);
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GeoHashRadius geohashGetAreasByRadiusMercator(double latitude, double longitude,
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double radius_meters);
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GeoHashFix52Bits geohashAlign52Bits(const GeoHashBits hash);
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double geohashGetXMercator(double longtitude);
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double geohashGetYMercator(double latitude);
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double geohashGetXWGS84(double x);
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double geohashGetYWGS84(double y);
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int geohashVerifyCoordinates(double x, double y);
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int geohashGetDistanceIfInRadius(double x1, double y1,
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double x2, double y2, double radius,
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double *distance);
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int geohashGetDistanceIfInRadiusWGS84(double x1, double y1, double x2,
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double y2, double radius,
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double *distance);
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int geohashGetDistanceSquaredIfInRadiusMercator(double x1, double y1,
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double x2, double y2,
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double radius,
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double *distance);
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#endif /* GEOHASH_HELPER_HPP_ */
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