2013/04/25 09:14

# geohash的算法

 纬度范围 划分区间0 划分区间1 39.92324所属区间 (-90, 90) (-90, 0.0) (0.0, 90) 1 (0.0, 90) (0.0, 45.0) (45.0, 90) 0 (0.0, 45.0) (0.0, 22.5) (22.5, 45.0) 1 (22.5, 45.0) (22.5, 33.75) (33.75, 45.0) 1 (33.75, 45.0) (33.75, 39.375) (39.375, 45.0) 1 (39.375, 45.0) (39.375, 42.1875) (42.1875, 45.0) 0 (39.375, 42.1875) (39.375, 40.7812) (40.7812, 42.1875) 0 (39.375, 40.7812) (39.375, 40.0781) (40.0781, 40.7812) 0 (39.375, 40.0781) (39.375, 39.7265) (39.7265, 40.0781) 1 (39.7265, 40.0781) (39.7265, 39.9023) (39.9023, 40.0781) 1 (39.9023, 40.0781) (39.9023, 39.9902) (39.9902, 40.0781) 0 (39.9023, 39.9902) (39.9023, 39.9462) (39.9462, 39.9902) 0 (39.9023, 39.9462) (39.9023, 39.9243) (39.9243, 39.9462) 0 (39.9023, 39.9243) (39.9023, 39.9133) (39.9133, 39.9243) 1 (39.9133, 39.9243) (39.9133, 39.9188) (39.9188, 39.9243) 1 (39.9188, 39.9243) (39.9188, 39.9215) (39.9215, 39.9243) 1

 经度范围 划分区间0 划分区间1 116.3906所属区间 (-180, 180) (-180, 0.0) (0.0, 180) 1 (0.0, 180) (0.0, 90.0) (90.0, 180) 1 (90.0, 180) (90.0, 135.0) (135.0, 180) 0 (90.0, 135.0) (90.0, 112.5) (112.5, 135.0) 1 (112.5, 135.0) (112.5, 123.75) (123.75, 135.0) 0 (112.5, 123.75) (112.5, 118.125) (118.125, 123.75) 0 (112.5, 118.125) (112.5, 115.312) (115.312, 118.125) 1 (115.312, 118.125) (115.312, 116.718) (116.718, 118.125) 0 (115.312, 116.718) (115.312, 116.015) (116.015, 116.718) 1 (116.015, 116.718) (116.015, 116.367) (116.367, 116.718) 1 (116.367, 116.718) (116.367, 116.542) (116.542, 116.718) 0 (116.367, 116.542) (116.367, 116.455) (116.455, 116.542) 0 (116.367, 116.455) (116.367, 116.411) (116.411, 116.455) 0 (116.367, 116.411) (116.367, 116.389) (116.389, 116.411) 1 (116.389, 116.411) (116.389, 116.400) (116.400, 116.411) 0 (116.389, 116.400) (116.389, 116.394) (116.394, 116.400) 0

 十进制 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 base32 0 1 2 3 4 5 6 7 8 9 b c d e f g 十进制 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 base32 h j k m n p q r s t u v w x y z

``````#define BASE32 "0123456789bcdefghjkmnpqrstuvwxyz"
static void encode_geohash(double latitude, double longitude, int precision, char *geohash) {
int is_even=1, i=0;
double lat[2], lon[2], mid;
char bits[] = {16,8,4,2,1};
int bit=0, ch=0;
lat[0] = -90.0; lat[1] = 90.0;
lon[0] = -180.0; lon[1] = 180.0;
while (i < precision) {
if (is_even) {
mid = (lon[0] + lon[1]) / 2;
if (longitude > mid) {
ch |= bits[bit];
lon[0] = mid;
} else
lon[1] = mid;
} else {
mid = (lat[0] + lat[1]) / 2;
if (latitude > mid) {
ch |= bits[bit];
lat[0] = mid;
} else
lat[1] = mid;
}
is_even = !is_even;
if (bit < 4)
bit++;
else {
geohash[i++] = BASE32[ch];
bit = 0;
ch = 0;
}
}
geohash[i] = 0;
}``````

0
1 收藏

0 评论
1 收藏
0