GeoHash 算法经纬度转换.docx

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1、GeoHash 算法经纬度转换欢迎登录清源教育官方网站 查看更多视频教程 GeoHash 算法 经纬度转换 geohash 在查找周围朋友，LBS中有很多的应用，在网上查找到geohash 算法实现分享给大家。 import java.util.HashMap; import java.util.Map; public class GeoHashKit / geohashs char map / no as is ls os / old MacDonal wouldnt be happy private static char _base32 = 0, 1, 2, 3, 4, 5, 6, 7,

2、 8, 9, b, c, d, e, f, g, h, j, k, m, n, p, q, r, s, t, u, v, w, x, y, z ; private final static Map _decodemap = new HashMap; static int sz = _base32.length; for (int i = 0; i sz; i+) _decodemap.put(_base32i, i); private static int precision = 12; private static int bits = 16, 8, 4, 2, 1 ; public sta

3、tic void main(String args) GeoHashKit ghf = new GeoHashKit; String gc1 = ghf.encode(31.277631, 120.53916300000003); String gc2 = ghf.encode(51.4797, -0.0124); System.out.println(gc1); System.out.println(gc2); double gd1 = ghf.decode(gc1); double gd2 = ghf.decode(gc2); System.out.println(gd10 + , + g

4、d11); System.out.println(gd20 + , + gd21); public static String encode(double latitude, double longitude) double lat_interval = -90.0, 90.0 ; double lon_interval = -180.0, 180.0 ; StringBuilder geohash = new StringBuilder; boolean is_even = true; int bit = 0, ch = 0; while (geohash.length mid) ch |=

5、 bitsbit; lon_interval0 = mid; else lon_interval1 = mid; else mid = (lat_interval0 + lat_interval1) / 2; if (latitude mid) ch |= bitsbit; lat_interval0 = mid; else lat_interval1 = mid; is_even = is_even ? false : true; if (bit 4) bit+; else geohash.append(_base32ch); bit = 0; ch = 0; return geohash.

6、toString; public static double decode(String geohash) double ge = decode_exactly(geohash); double lat, lon, lat_err, lon_err; lat = ge0; lon = ge1; lat_err = ge2; lon_err = ge3; double lat_precision = Math.max(1, Math.round(-Math.log10(lat_err) - 1; double lon_precision = Math.max(1, Math.round(-Mat

7、h.log10(lon_err) - 1; lat = getPrecision(lat, lat_precision); lon = getPrecision(lon, lon_precision); return new double lat, lon ; public static double decode_exactly(String geohash) double lat_interval = -90.0, 90.0 ; double lon_interval = -180.0, 180.0 ; double lat_err = 90.0; double lon_err = 180

8、.0; 欢迎登录清源教育官方网站 查看更多视频教程 boolean is_even = true; int sz = geohash.length; int bsz = bits.length; double latitude, longitude; for (int i = 0; i sz; i+) int cd = _decodemap.get(geohash.charAt(i); for (int z = 0; z bsz; z+) int mask = bitsz; if (is_even) lon_err /= 2; if (cd & mask) != 0) lon_interval

9、0 = (lon_interval0 + lon_interval1) / 2; else lon_interval1 = (lon_interval0 + lon_interval1) / 2; else lat_err /= 2; if (cd & mask) != 0) lat_interval0 = (lat_interval0 + lat_interval1) / 2; else lat_interval1 = (lat_interval0 + lat_interval1) / 2; is_even = is_even ? false : true; latitude = (lat_interval0 + lat_interval1) / 2; longitude = (lon_interval0 + lon_interval1) / 2; return new double latitude, longitude, lat_err, lon_err ; static double getPrecision(double x, double precision) double base = Math.pow(10, -precision); double diff = x % base; return x - diff; 来源：清源教育