GeoHash算法与用法

浅浅的花香味﹌ 2023-02-10 05:12 57阅读 0赞

/**
     * GeoHash算法
     *
     * 可以到 http://geohash.co/ 进行geohash编码，以确定自己代码是否写错
     *
     * @Description  GeoHash字符串编码越长，表示的范围越小，位置也越精确。
     * 因此我们就可以通过比较GeoHash匹配的位数来判断两个点之间的大概距离。
     * @author xrj
     * @date 2020/4/15
     */
    @Slf4j
    public class GeoHash {
     
        private static final double MINLAT = -90;
        private static final double MAXLAT = 90;
        private static final double MINLNG = -180;
        private static final double MAXLNG = 180;
     
        private final static char[] digits = { '0', '1', '2', '3', '4', '5', '6', '7', '8',
                '9', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k', 'm', 'n', 'p',
                'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };
     
        //定义编码映射关系
        private final static HashMap<Character, Integer> lookup = new HashMap<Character, Integer>();
        //初始化编码映射内容
        static {
            int i = 0;
            for (char c : digits)
                lookup.put(c, i++);
        }
     
        /**
         * 范围最小
         */
        private static final int SCOPE_MIX=6;
        private static final int MULTIPLE=5;
     
     
     
        /**
         * 范围最小是3   1.2km
         * 范围一般是2   39.1km
         * 范围最大是1   5000km
         * current_numbits=数字*5
         * current_numbits=SCOPE_MIX*MULTIPLE
         */
        private  int current_numbits ;
     
        //最小单位
        private  double minLat;
        private  double minLng;
     
        /**
         * 私有化构造器
         */
        private GeoHash(){
     
        }
     
        /**
         * 模糊匹配
         * 必须赋值经纬度单独编码长度，否则报错
         * @param numbits 整数范围1-3；包含1和3
         * 范围最小是3   1.2km
         * 范围一般是2   39.1km
         * 范围最大是1   5000km
         */
        private GeoHash(Integer numbits){
            if(numbits!=null && numbits>0 && numbits<4){
                this.current_numbits=numbits*MULTIPLE;
                setMinLatLng();
            }else{
                throw new BaseException(Constant.BUSINESS,ResultEnum.GEOHASH_FAILED);
            }
        }
        /**
         * 得到了最小单位，那么周边区域的经纬度也可以计算得到了。比如说左边区域的经度肯定是自身经度减去最小经度单位。
         * 纬度也可以通过加减，得到上下的纬度值，最终周围8个单位也可以计算得到。
         */
        private void setMinLatLng() {
            minLat = MAXLAT - MINLAT;
            for (int i = 0; i < current_numbits; i++) {
                minLat /= 2.0;
            }
            minLng = MAXLNG - MINLNG;
            for (int i = 0; i < current_numbits; i++) {
                minLng /= 2.0;
            }
        }
        /**
         * 企业，项目，消纳站得到geoHash参数
         * @param lat 纬度
         * @param lon 经度
         * @return
         */
        public static String getGeoHashStr(Double lat, Double lon){
            validatorParam(lon,lat);
            return new GeoHash(SCOPE_MIX).encode(lat,lon);
        }
        /**
         * 得到模糊查询的geohash字符串
         * 范围最小是3   1.2km
         * 范围一般是2   39.1km
         * 范围最大是1   5000km
         * @param lat 纬度
         * @param lon 经度
         * @return
         */
        public static String getGeoHashByLikeStr(Integer scope,Double lat, Double lon){
            validatorParam(lon,lat);
            return new GeoHash(scope).encode(lat,lon);
        }
        /**
         * 得到附近八个点
         * 范围最小是3   1.2km
         * 范围一般是2   39.1km
         * 范围最大是1   5000km
         * @param lat 纬度
         * @param lon 经度
         * @return
         */
        public static ArrayList<String> getArroundGeoHashByLikeStr(Integer scope,Double lat, Double lon){
             validatorParam(lon,lat);
            return new GeoHash(scope).getArroundGeoHash(lat,lon);
        }
     
     
        /**
         * 对geoHashStr接码得到经纬度
         * @param geoHashStr
         * @return
         */
        public static double[] getDecodeByGeoHashStr(String geoHashStr){
            return new GeoHash(SCOPE_MIX).decode(geoHashStr);
        }
     
     
        private static void validatorParam(Double lon,Double lat){
             if(lon == null || lon==0 || lat==null || lat==0){
             //抛异常
           }
        }
     
        /**
         * 得到GeoHash字符串
         * @param lat   纬度
         * @param lon   经度
         * @return
         */
        private String encode(double lat, double lon) {
            BitSet latbits = getBits(lat, MINLAT, MAXLAT);
            BitSet lonbits = getBits(lon, MINLNG, MAXLNG);
            StringBuilder buffer = new StringBuilder();
            for (int i = 0; i < current_numbits; i++) {
                buffer.append( (lonbits.get(i))?'1':'0');
                buffer.append( (latbits.get(i))?'1':'0');
            }
            String code = base32(Long.parseLong(buffer.toString(), 2));
            log.info( "encode  lat = " + lat + "  lng = " + lon + "  code = " + code);
            return code;
        }
        /**
         * 根据经纬度和范围，获取对应的二进制
         * @param lat
         * @param floor
         * @param ceiling
         * @return
         */
        private BitSet getBits(double lat, double floor, double ceiling) {
            BitSet buffer = new BitSet(current_numbits);
            for (int i = 0; i < current_numbits; i++) {
                double mid = (floor + ceiling) / 2;
                if (lat >= mid) {
                    buffer.set(i);
                    floor = mid;
                } else {
                    ceiling = mid;
                }
            }
            return buffer;
        }
        /**
         * 将经纬度合并后的二进制进行指定的32位编码
         * @param i
         * @return
         */
        private String base32(long i) {
            char[] buf = new char[65];
            int charPos = 64;
            boolean negative = (i < 0);
            if (!negative){
                i = -i;
            }
            while (i <= -32) {
                buf[charPos--] = digits[(int) (-(i % 32))];
                i /= 32;
            }
            buf[charPos] = digits[(int) (-i)];
            if (negative){
                buf[--charPos] = '-';
            }
            return new String(buf, charPos, (65 - charPos));
        }
        /**
         * 对编码后的字符串解码得到经纬度
         * @param geohash
         * @return
         */
        private double[] decode(String geohash) {
            StringBuilder buffer = new StringBuilder();
            for (char c : geohash.toCharArray()) {
                int i = lookup.get(c) + 32;
                buffer.append( Integer.toString(i, 2).substring(1) );
            }
            BitSet lonset = new BitSet();
            BitSet latset = new BitSet();
            //偶数位，经度
            int j =0;
            for (int i=0; i< current_numbits*2;i+=2) {
                boolean isSet = false;
                if ( i < buffer.length() )
                    isSet = buffer.charAt(i) == '1';
                lonset.set(j++, isSet);
            }
            //奇数位，纬度
            j=0;
            for (int i=1; i< current_numbits*2;i+=2) {
                boolean isSet = false;
                if ( i < buffer.length() )
                    isSet = buffer.charAt(i) == '1';
                latset.set(j++, isSet);
            }
            double lon = decode(lonset, -180, 180);
            double lat = decode(latset, -90, 90);
            return new double[] {lat, lon};
        }
        /**
         * 根据二进制和范围解码
         * @param bs
         * @param floor
         * @param ceiling
         * @return
         */
        private double decode(BitSet bs, double floor, double ceiling) {
            double mid = 0;
            for (int i=0; i<bs.length(); i++) {
                mid = (floor + ceiling) / 2;
                if (bs.get(i))
                    floor = mid;
                else
                    ceiling = mid;
            }
            return mid;
        }
        /**
         * 得到附近八个点
         * @param lat
         * @param lon
         * @return
         */
        private ArrayList<String> getArroundGeoHash(double lat, double lon){
            log.info("getArroundGeoHash  lat = " + lat + "  lng = " + lon);
            ArrayList<String> list = new ArrayList<>();
            double uplat = lat + minLat;
            double downLat = lat - minLat;
            double leftlng = lon - minLng;
            double rightLng = lon + minLng;
            String leftUp = encode(uplat, leftlng);
            list.add(leftUp);
            String leftMid = encode(lat, leftlng);
            list.add(leftMid);
            String leftDown = encode(downLat, leftlng);
            list.add(leftDown);
            String midUp = encode(uplat, lon);
            list.add(midUp);
            String midMid = encode(lat, lon);
            list.add(midMid);
            String midDown = encode(downLat, lon);
            list.add(midDown);
            String rightUp = encode(uplat, rightLng);
            list.add(rightUp);
            String rightMid = encode(lat, rightLng);
            list.add(rightMid);
            String rightDown = encode(downLat, rightLng);
            list.add(rightDown);
            log.info("getArroundGeoHash list = " + list.toString());
            return list;
        }
        public static void main(String[] args)  throws Exception{
            //得到建筑物当前矩形点位
            String s = getGeoHashStr(40.222012, 116.248283);
            System.out.println("字符串："+s);
            //得到范围比较大的点位
    //        System.out.println(getGeoHashByLikeStr(3,40.222012, 116.248283));
    //        //查询最近的点
    //        getArroundGeoHashByLikeStr(SCOPE_MIX,40.222012, 116.248283);
    //        getArroundGeoHashByLikeStr(5,40.222012, 116.248283);
    //        //得到经纬度
            double[] geo = getDecodeByGeoHashStr(s);
            System.out.println(geo[0]+" "+geo[1]);
        }
    }

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