1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
|
/*
* Copyright (c) 2013-2014, yinqiwen <yinqiwen@gmail.com>
* Copyright (c) 2014, Matt Stancliff <matt@genges.com>.
* Copyright (c) 2015-2016, Salvatore Sanfilippo <antirez@gmail.com>.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
/* This is a C++ to C conversion from the ardb project.
* This file started out as:
* https://github.com/yinqiwen/ardb/blob/d42503/src/geo/geohash_helper.cpp
*/
#include "fmacros.h"
#include "geohash_helper.h"
#include "debugmacro.h"
#include <math.h>
#define D_R (M_PI / 180.0)
#define R_MAJOR 6378137.0
#define R_MINOR 6356752.3142
#define RATIO (R_MINOR / R_MAJOR)
#define ECCENT (sqrt(1.0 - (RATIO *RATIO)))
#define COM (0.5 * ECCENT)
/// @brief The usual PI/180 constant
const double DEG_TO_RAD = 0.017453292519943295769236907684886;
/// @brief Earth's quatratic mean radius for WGS-84
const double EARTH_RADIUS_IN_METERS = 6372797.560856;
const double MERCATOR_MAX = 20037726.37;
const double MERCATOR_MIN = -20037726.37;
static inline double deg_rad(double ang) { return ang * D_R; }
static inline double rad_deg(double ang) { return ang / D_R; }
/* This function is used in order to estimate the step (bits precision)
* of the 9 search area boxes during radius queries. */
uint8_t geohashEstimateStepsByRadius(double range_meters, double lat) {
if (range_meters == 0) return 26;
int step = 1;
while (range_meters < MERCATOR_MAX) {
range_meters *= 2;
step++;
}
step -= 2; /* Make sure range is included in most of the base cases. */
/* Wider range torwards the poles... Note: it is possible to do better
* than this approximation by computing the distance between meridians
* at this latitude, but this does the trick for now. */
if (lat > 66 || lat < -66) {
step--;
if (lat > 80 || lat < -80) step--;
}
/* Frame to valid range. */
if (step < 1) step = 1;
if (step > 26) step = 26;
return step;
}
/* Return the bounding box of the search area centered at latitude,longitude
* having a radius of radius_meter. bounds[0] - bounds[2] is the minimum
* and maxium longitude, while bounds[1] - bounds[3] is the minimum and
* maximum latitude.
*
* This function does not behave correctly with very large radius values, for
* instance for the coordinates 81.634948934258375 30.561509253718668 and a
* radius of 7083 kilometers, it reports as bounding boxes:
*
* min_lon 7.680495, min_lat -33.119473, max_lon 155.589402, max_lat 94.242491
*
* However, for instance, a min_lon of 7.680495 is not correct, because the
* point -1.27579540014266968 61.33421815228281559 is at less than 7000
* kilometers away.
*
* Since this function is currently only used as an optimization, the
* optimization is not used for very big radiuses, however the function
* should be fixed. */
int geohashBoundingBox(double longitude, double latitude, double radius_meters,
double *bounds) {
if (!bounds) return 0;
bounds[0] = longitude - rad_deg(radius_meters/EARTH_RADIUS_IN_METERS/cos(deg_rad(latitude)));
bounds[2] = longitude + rad_deg(radius_meters/EARTH_RADIUS_IN_METERS/cos(deg_rad(latitude)));
bounds[1] = latitude - rad_deg(radius_meters/EARTH_RADIUS_IN_METERS);
bounds[3] = latitude + rad_deg(radius_meters/EARTH_RADIUS_IN_METERS);
return 1;
}
/* Return a set of areas (center + 8) that are able to cover a range query
* for the specified position and radius. */
GeoHashRadius geohashGetAreasByRadius(double longitude, double latitude, double radius_meters) {
GeoHashRange long_range, lat_range;
GeoHashRadius radius;
GeoHashBits hash;
GeoHashNeighbors neighbors;
GeoHashArea area;
double min_lon, max_lon, min_lat, max_lat;
double bounds[4];
int steps;
geohashBoundingBox(longitude, latitude, radius_meters, bounds);
min_lon = bounds[0];
min_lat = bounds[1];
max_lon = bounds[2];
max_lat = bounds[3];
steps = geohashEstimateStepsByRadius(radius_meters,latitude);
geohashGetCoordRange(&long_range,&lat_range);
geohashEncode(&long_range,&lat_range,longitude,latitude,steps,&hash);
geohashNeighbors(&hash,&neighbors);
geohashDecode(long_range,lat_range,hash,&area);
/* Check if the step is enough at the limits of the covered area.
* Sometimes when the search area is near an edge of the
* area, the estimated step is not small enough, since one of the
* north / south / west / east square is too near to the search area
* to cover everything. */
int decrease_step = 0;
{
GeoHashArea north, south, east, west;
geohashDecode(long_range, lat_range, neighbors.north, &north);
geohashDecode(long_range, lat_range, neighbors.south, &south);
geohashDecode(long_range, lat_range, neighbors.east, &east);
geohashDecode(long_range, lat_range, neighbors.west, &west);
if (geohashGetDistance(longitude,latitude,longitude,north.latitude.max)
< radius_meters) decrease_step = 1;
if (geohashGetDistance(longitude,latitude,longitude,south.latitude.min)
< radius_meters) decrease_step = 1;
if (geohashGetDistance(longitude,latitude,east.longitude.max,latitude)
< radius_meters) decrease_step = 1;
if (geohashGetDistance(longitude,latitude,west.longitude.min,latitude)
< radius_meters) decrease_step = 1;
}
if (steps > 1 && decrease_step) {
steps--;
geohashEncode(&long_range,&lat_range,longitude,latitude,steps,&hash);
geohashNeighbors(&hash,&neighbors);
geohashDecode(long_range,lat_range,hash,&area);
}
/* Exclude the search areas that are useless. */
if (steps >= 2) {
if (area.latitude.min < min_lat) {
GZERO(neighbors.south);
GZERO(neighbors.south_west);
GZERO(neighbors.south_east);
}
if (area.latitude.max > max_lat) {
GZERO(neighbors.north);
GZERO(neighbors.north_east);
GZERO(neighbors.north_west);
}
if (area.longitude.min < min_lon) {
GZERO(neighbors.west);
GZERO(neighbors.south_west);
GZERO(neighbors.north_west);
}
if (area.longitude.max > max_lon) {
GZERO(neighbors.east);
GZERO(neighbors.south_east);
GZERO(neighbors.north_east);
}
}
radius.hash = hash;
radius.neighbors = neighbors;
radius.area = area;
return radius;
}
GeoHashRadius geohashGetAreasByRadiusWGS84(double longitude, double latitude,
double radius_meters) {
return geohashGetAreasByRadius(longitude, latitude, radius_meters);
}
GeoHashFix52Bits geohashAlign52Bits(const GeoHashBits hash) {
uint64_t bits = hash.bits;
bits <<= (52 - hash.step * 2);
return bits;
}
/* Calculate distance using haversin great circle distance formula. */
double geohashGetDistance(double lon1d, double lat1d, double lon2d, double lat2d) {
double lat1r, lon1r, lat2r, lon2r, u, v;
lat1r = deg_rad(lat1d);
lon1r = deg_rad(lon1d);
lat2r = deg_rad(lat2d);
lon2r = deg_rad(lon2d);
u = sin((lat2r - lat1r) / 2);
v = sin((lon2r - lon1r) / 2);
return 2.0 * EARTH_RADIUS_IN_METERS *
asin(sqrt(u * u + cos(lat1r) * cos(lat2r) * v * v));
}
int geohashGetDistanceIfInRadius(double x1, double y1,
double x2, double y2, double radius,
double *distance) {
*distance = geohashGetDistance(x1, y1, x2, y2);
if (*distance > radius) return 0;
return 1;
}
int geohashGetDistanceIfInRadiusWGS84(double x1, double y1, double x2,
double y2, double radius,
double *distance) {
return geohashGetDistanceIfInRadius(x1, y1, x2, y2, radius, distance);
}
|
