離我最近之geohash算法（增加周邊鄰近編號(hào)）

發(fā)表時(shí)間：2020-10-19

發(fā)布人：葵宇科技

瀏覽次數(shù)：60

接著上一篇文┞仿：查找鄰近網(wǎng)點(diǎn)geohash算法及實(shí)現(xiàn) （Java版本） http://blog.csdn.net/sunrise_2013/article/details/42024813
參考文檔：
http://www.slideshare.net/sandeepbhaskar2/geohash 介紹geohash道理及例子
http://geohash.gofreerange.com/ 演示實(shí)例
http://geohash.gofreerange.com/ 周邊8格子實(shí)例
因?yàn)榇嬖诔志W(wǎng)點(diǎn)損掉的情況，為懂得決邊沿問(wèn)題，須要計(jì)算這個(gè)塊四周的八個(gè)格子，彌補(bǔ)代碼，實(shí)現(xiàn)周邊8個(gè)編碼的比來(lái)編碼。
根據(jù)一個(gè)geohash值獲取四周8個(gè)geohash值的代碼。
例如在方格4的左下部分的點(diǎn)和大年夜方格1的右下部分的點(diǎn)離的很近，可是它們的geohash值必定是相差的相當(dāng)遠(yuǎn)，因?yàn)轭^一次的分塊就相差太大年夜了，很多時(shí)刻我們對(duì)geohash的值進(jìn)內(nèi)行單的排序比較，結(jié)不雅貌似真的可以或許找出鄰近的點(diǎn)，并且似乎照樣按照距離的遠(yuǎn)近分列的，可是實(shí)際上會(huì)有一些點(diǎn)被漏掉落了。
上述這個(gè)問(wèn)題，可以經(jīng)由過(guò)程搜刮一個(gè)格子，四周八個(gè)格子的數(shù)據(jù)，同一獲取后再進(jìn)行過(guò)濾。如許就在編碼條懂得決了這個(gè)問(wèn)題。
[img]http://img.blog.csdn.net/20150105090803059?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3VucmlzZV8yMDEz/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center
全部代碼實(shí)例：
Geohase.java

package com.DistTest;

//Geohash.java
//Geohash library for Java
//ported from David Troy's Geohash library for Javascript
//- http://github.com/davetroy/geohash-js/tree/master
//(c) 2008 David Troy
//(c) 2008 Tom Carden
//Distributed under the MIT License

public class Geohash {

     public static int BITS[] = { 16, 8, 4, 2, 1 };

     public static String BASE32 = "0123456789bcdefghjkmnpqrstuvwxyz";

     public static int RIGHT = 0;
     public static int LEFT = 1;
     public static int TOP = 2;
     public static int BOTTOM = 3;

     public static int EVEN = 0;
     public static int ODD = 1;

     public static String[][] NEIGHBORS;
     public static String[][] BORDERS;

     static {
             NEIGHBORS = new String[4][2];
             BORDERS = new String[4][2];

             NEIGHBORS[BOTTOM][EVEN] = "bc01fg45238967deuvhjyznpkmstqrwx";
             NEIGHBORS[TOP][EVEN] = "238967debc01fg45kmstqrwxuvhjyznp";
             NEIGHBORS[LEFT][EVEN] = "p0r21436x8zb9dcf5h7kjnmqesgutwvy";
             NEIGHBORS[RIGHT][EVEN] = "14365h7k9dcfesgujnmqp0r2twvyx8zb";

             BORDERS[BOTTOM][EVEN] = "bcfguvyz";
             BORDERS[TOP][EVEN] = "0145hjnp";
             BORDERS[LEFT][EVEN] = "prxz";
             BORDERS[RIGHT][EVEN] = "028b";

             NEIGHBORS[BOTTOM][ODD] = NEIGHBORS[LEFT][EVEN];
             NEIGHBORS[TOP][ODD] = NEIGHBORS[RIGHT][EVEN];
             NEIGHBORS[LEFT][ODD] = NEIGHBORS[BOTTOM][EVEN];
             NEIGHBORS[RIGHT][ODD] = NEIGHBORS[TOP][EVEN];

             BORDERS[BOTTOM][ODD] = BORDERS[LEFT][EVEN];
             BORDERS[TOP][ODD] = BORDERS[RIGHT][EVEN];
             BORDERS[LEFT][ODD] = BORDERS[BOTTOM][EVEN];
             BORDERS[RIGHT][ODD] = BORDERS[TOP][EVEN];
     }

     private static void refine_interval(double[] interval, int cd, int mask) {
             if ((cd & mask) > 0) {
                     interval[0] = (interval[0] + interval[1]) / 2.0;
             } else {
                     interval[1] = (interval[0] + interval[1]) / 2.0;
             }
     }

     public static String calculateAdjacent(String srcHash, int dir) {
             srcHash = srcHash.toLowerCase();
             char lastChr = srcHash.charAt(srcHash.length() - 1);
             int type = (srcHash.length() % 2) == 1 ? ODD : EVEN;
             String base = srcHash.substring(0, srcHash.length() - 1);
             if (BORDERS[dir][type].indexOf(lastChr) != -1) {
                     base = calculateAdjacent(base, dir);
             }
             return base + BASE32.charAt(NEIGHBORS[dir][type].indexOf(lastChr));
     }
     
     
     

 	public static String[] getGeoHashExpand(String geohash) {
 		try {
 			String geohashTop = calculateAdjacent(geohash, TOP);
 			String geohashBottom = calculateAdjacent(geohash, BOTTOM);
 			String geohashRight = calculateAdjacent(geohash, RIGHT);
 			String geohashLeft = calculateAdjacent(geohash, LEFT);
 	
 			String geohashTopLeft = calculateAdjacent(geohashLeft, TOP);
 			String geohashTopRight = calculateAdjacent(geohashRight, TOP);
 			String geohashBottomRight = calculateAdjacent(geohashRight, BOTTOM);
 			String geohashBottomLeft = calculateAdjacent(geohashLeft, BOTTOM);
 	
 			String[] expand = { geohash, geohashTop, geohashBottom, geohashRight, geohashLeft, geohashTopLeft,
 					geohashTopRight, geohashBottomRight, geohashBottomLeft };
 			return expand;
 		} catch (Exception e) {
 			//logger.error("GeoHash Error",e);
 			return null;
 		}
 	}
     

     public static double[][] decode(String geohash) {
             boolean is_even = true;
             double[] lat = new double[3];
             double[] lon = new double[3];

             lat[0] = -90.0;
             lat[1] = 90.0;
             lon[0] = -180.0;
             lon[1] = 180.0;
             double lat_err = 90.0;
             double lon_err = 180.0;

             for (int i = 0; i < geohash.length(); i++) {
                     char c = geohash.charAt(i);
                     int cd = BASE32.indexOf(c);
                     for (int j = 0; j < BITS.length; j++) {
                             int mask = BITS[j];
                             if (is_even) {
                                     lon_err /= 2.0;
                                     refine_interval(lon, cd, mask);
                             } else {
                                     lat_err /= 2.0;
                                     refine_interval(lat, cd, mask);
                             }
                             is_even = !is_even;
                     }
             }
             lat[2] = (lat[0] + lat[1]) / 2.0;
             lon[2] = (lon[0] + lon[1]) / 2.0;

             return new double[][] { lat, lon };
     }

     public static String encode(double latitude, double longitude) {
             boolean is_even = true;
             int i = 0;
             double lat[] = new double[3];
             double lon[] = new double[3];
             int bit = 0;
             int ch = 0;
             int precision = 12;
             String geohash = "";

             lat[0] = -90.0;
             lat[1] = 90.0;
             lon[0] = -180.0;
             lon[1] = 180.0;

             while (geohash.length() < precision) {
                     if (is_even) {
                             double mid = (lon[0] + lon[1]) / 2.0;
                             if (longitude > mid) {
                                     ch |= BITS[bit];
                                     lon[0] = mid;
                             } else {
                                     lon[1] = mid;
                             }
                     } else {
                             double mid = (lat[0] + lat[1]) / 2.0;
                             if (latitude > mid) {
                                     ch |= BITS[bit];
                                     lat[0] = mid;
                             } else {
                                     lat[1] = mid;
                             }
                     }
                     is_even = !is_even;
                     if (bit < 4) {
                             bit++;
                     } else {
                             geohash += BASE32.charAt(ch);
                             bit = 0;
                             ch = 0;
                     }
             }
             return geohash;
     }

}

測(cè)試實(shí)例：

package com.DistTest;
  
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Connection;
import java.sql.Statement;
 
 
public class sqlTest {
	
        public static void main(String[] args) throws Exception {
        Connection conn = null;
        String sql;
        String sql1;
        String url = "jdbc:mysql://132.97.194.62/test?"
                + "user=root&password=sheng&useUnicode=true&characterEncoding=UTF8";
 
        try {
            Class.forName("com.mysql.jdbc.Driver");// 動(dòng)態(tài)加載mysql驅(qū)動(dòng)
            // System.out.println("成功加載MySQL驅(qū)動(dòng)法度榜樣");
            // 一個(gè)Connection代表一個(gè)數(shù)據(jù)庫(kù)連接
            conn = DriverManager.getConnection(url);
            // Statement瑯綾擎帶有很多辦法，比如executeUpdate可以實(shí)現(xiàn)插入，更新和刪除等
            Statement stmt = conn.createStatement();
                               
	  	    double lon1=109.0145193757;  
	  	    double lat1=34.236080797698;
	  	    //根據(jù)地輿坐標(biāo)，生成geohash編碼
      	   // Geohash ghash = new Geohash();
    	   // String gcode=Geohash.encode(lat1, lon1).substring(0, 4);
      	    String gcode="wqj6z";
      	    
      	    String[] neargcode=Geohash.getGeoHashExpand(gcode);
      	    
	      	  for(int i=0;i<neargcode.length;i++)
	      	{
	      		System.out.println(neargcode[i]);
	      	}

            sql = "select * from retailersinfotable where geohash like "
            		+ "'"+neargcode[0]+"%' or '"+neargcode[1]+"%' or '"+neargcode[2]+"%' "
            		+ "or '"+neargcode[3]+"%' or '"+neargcode[4]+"%' or '"+neargcode[5]+"%' "
            		+ "or '"+neargcode[6]+"%' or '"+neargcode[7]+"%' or '"+neargcode[8]+"%'";
            System.out.println(sql);
            ResultSet rs = stmt.executeQuery(sql);// executeQuery會(huì)返回結(jié)不雅的集合，不然返回空值
            rs.last();
            int rowCount = rs.getRow(); //獲得ResultSet的總行數(shù)
            System.out.println(rowCount);
            rs.beforeFirst();
            
            System.out.println("當(dāng)前地位：經(jīng)度"+lon1+" 維度："+lat1);
            int i=0;
    		String[][] array = new String[rowCount][3];
            while (rs.next()){
            		//大年夜數(shù)據(jù)庫(kù)掏出地輿坐標(biāo)
            		double lon2=Double.parseDouble(rs.getString("Longitude"));
            		double lat2=Double.parseDouble(rs.getString("Latitude"));
            		
            		//根據(jù)地輿坐標(biāo)，生成geohash編碼
	          	    Geohash geohash = new Geohash();
	        	    String geocode=geohash.encode(lat2, lon2).substring(0, 9);
	        	    
	        	    //計(jì)算兩點(diǎn)間的距離
	      	        int dist=(int) Test.GetDistance(lon1, lat1, lon2, lat2); 
	      	        
	      			array[i][0]=String.valueOf(i);
	    			array[i][1]=geocode;
	    			array[i][2]=Integer.toString(dist);
	      			
	      			i++;
        
            	//	System.out.println(lon2+"---"+lat2+"---"+geocode+"---"+dist);	
                }

            array=sqlTest.getOrder(array); //二維數(shù)組排序
            sqlTest.showArray(array);        //打印數(shù)組

            
            
            
        } catch (SQLException e) {
            System.out.println("MySQL操作缺點(diǎn)");
            e.printStackTrace();
        } finally {
            conn.close();
        }
 
    } 
    /*
     * 二維數(shù)組排序，比較array[][2]的值，返回二維數(shù)組
     * */
    public static String[][] getOrder(String[][] array){
		for (int j = 0; j < array.length ; j++) {
			for (int bb = 0; bb < array.length - 1; bb++) {
				String[] ss;
				int a1=Integer.valueOf(array[bb][2]);  //轉(zhuǎn)化成int型比較大年夜小
				int a2=Integer.valueOf(array[bb+1][2]);
				if (a1>a2) {
					ss = array[bb];
					array[bb] = array[bb + 1];
					array[bb + 1] = ss;
					
				}
			}
		} 
		return array;
    }
    
    /*打印數(shù)組*/
    public static void showArray(String[][] array){
    	  for(int a=0;a<array.length;a++){
      		for(int j=0;j<array[0].length;j++)
      			System.out.print(array[a][j]+" ");
      		System.out.println();
      	}
    }

 /*   public static void main(String[] args)
    {
    	String aaa="wxsfdf";
    	Geohash geohash = new Geohash();
    	String[] str = geohash.getGeoHashExpand(aaa);
    	for(int i=0;i<str.length;i++)
    	{
    		System.out.println(str[i]);
    	}
    
    }*/
    
}