火星坐标

package com.hac.util;

import java.text.DecimalFormat;
import java.util.BitSet;
import java.util.HashMap;

/**
 * geohash 经纬度转换
 * @author zhaoxueyuan
 *
 */
public class GeohashUtil {
    private static int numbits = 6 * 5;
    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‘ };

    final static HashMap<Character, Integer> lookup = new HashMap<Character, Integer>();
    static {
        int i = 0;
        for (char c : digits) {
            lookup.put(c, i++);
        }
    }

    public static void main(String[] args) {
        double[] latlon = new GeohashUtil().decode("dj248j248j24");
        System.out.println(latlon[0] + " " + latlon[1]);

        GeohashUtil e = new GeohashUtil();
        String s = e.encode(30, -90.0);
        System.out.println(s);
        latlon = e.decode(s);
        DecimalFormat df = new DecimalFormat("0.00000");
        System.out.println(df.format(latlon[0]) + ", " + df.format(latlon[1]));

    }

    /**
     * 将Geohash字串解码成经纬值
     *
     * @param geohash
     *            待解码的Geohash字串
     * @return 经纬值数组
     */
    public static 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();

        // even bits
        int j = 0;
        for (int i = 0; i < numbits * 2; i += 2) {
            boolean isSet = false;
            if (i < buffer.length())
                isSet = buffer.charAt(i) == ‘1‘;
            lonset.set(j++, isSet);
        }

        // odd bits
        j = 0;
        for (int i = 1; i < numbits * 2; i += 2) {
            boolean isSet = false;
            if (i < buffer.length())
                isSet = buffer.charAt(i) == ‘1‘;
            latset.set(j++, isSet);
        }

        double lat = decode(latset, -90, 90);
        double lon = decode(lonset, -180, 180);

        DecimalFormat df = new DecimalFormat("0.00000");
        return new double[] { Double.parseDouble(df.format(lat)), Double.parseDouble(df.format(lon)) };
    }

    /**
     * 根据二进制编码串和指定的数值变化范围，计算得到经/纬值
     *
     * @param bs
     *            经/纬二进制编码串
     * @param floor
     *            下限
     * @param ceiling
     *            上限
     * @return 经/纬值
     */
    private static 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;
    }

    /**
     * 根据经纬值得到Geohash字串
     *
     * @param lat
     *            纬度值
     * @param lon
     *            经度值
     * @return Geohash字串
     */
    public static String encode(double lat, double lon) {
        BitSet latbits = getBits(lat, -90, 90);
        BitSet lonbits = getBits(lon, -180, 180);
        StringBuilder buffer = new StringBuilder();
        for (int i = 0; i < numbits; i++) {
            buffer.append((lonbits.get(i)) ? ‘1‘ : ‘0‘);
            buffer.append((latbits.get(i)) ? ‘1‘ : ‘0‘);
        }
        return base32(Long.parseLong(buffer.toString(), 2));
    }

    /**
     * 将二进制编码串转换成Geohash字串
     *
     * @param i
     *            二进制编码串
     * @return Geohash字串
     */
    public static 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));
    }

    /**
     * 得到经/纬度对应的二进制编码
     *
     * @param lat
     *            经/纬度
     * @param floor
     *            下限
     * @param ceiling
     *            上限
     * @return 二进制编码串
     */
    private static BitSet getBits(double lat, double floor, double ceiling) {
        BitSet buffer = new BitSet(numbits);
        for (int i = 0; i < numbits; i++) {
            double mid = (floor + ceiling) / 2;
            if (lat >= mid) {
                buffer.set(i);
                floor = mid;
            } else {
                ceiling = mid;
            }
        }
        return buffer;
    }

}