Search for people near by latitude, and a simple implementation of distance sorting.

search for people near by latitude, and simple implementation by distance sorting

This is a simple implementation, the small amount of data can still meet the demand, write here to make a record. Of course, I hope there are other better options.

The main idea is: first, with their latitude and longitude as the center, the calculation of a certain radius of the square latitude and longitude boundary, and then use the square latitude and longitude boundary filter the user, and use a calculation of two points between the distance between the custom database function calculation distance, and then calculate the distance in reverse order calculate the square latitude and longitude in a certain radius

Long Raidus = 10000; Radius 10km double lat = 23.155778; Current Latitude Double lon = 113.262744;
Current longitude map<string, object> param = new hashmap<> ();
Param.put ("lat", lat);

Param.put ("Lon", Lon); private void Loadgeosquare (map<string, object> parm, double lat, double lon, long Raidus) {Double latitude = lat    
    ;    

    Double longitude = lon;    
    The equator circumference 24901 miles 1609 is the coefficient of conversion into a meter Double degree = (24901 * 1609)/360.0;    

    Double raidusmile = Raidus;    
    Double Dpmlat = 1/degree;    
    Double Radiuslat = Dpmlat * raidusmile;    
    Double Minlat = Latitude-radiuslat;    

    Double Maxlat = latitude + Radiuslat;    
    Double mpdlng = degree * Math.Cos (latitude * (math.pi/180));                 
    Double dpmlng = 1/mpdlng;     
    Double radiuslng = dpmlng * raidusmile;      
    Double minlng = longitude-radiuslng;      
    Double maxlng = longitude + radiuslng;
    return new double[] {Minlat, minlng, Maxlat, maxlng}; Parm.put ("MinlAt ", Minlat);
    Parm.put ("Minlng", MINLNG);
    Parm.put ("Maxlat", Maxlat);
Parm.put ("Maxlng", MAXLNG); }

SQL Calculations

I use the mybatis, of course, SQL we should all be able to read

<select id= "Querynearbypage" resulttype= "Appusernearby" >
    select ID, Avatar, nickname, sex, Birthday, Lovecode,
    ROUND (Lat_lng_distance (#{lat}, #{lon}, lat, lon), 2 as distance from 
    zan_user zuser 
    WHERE 
    <! [cdata[and Lat > #{minlat} and Lat < #{maxlat} and Lon > #{minlng} and Lon < #{maxlng}]]> order by
    di Stance ASC 
    LIMIT #{rowstart},#{rowend}
</select>

The database function, which calculates the distance between two latitude and longitude, is also posted here:

CREATE FUNCTION ' lat_lng_distance ' (lat1 float, lng1 float, lat2 float, lng2 float)
RETURNS float
deterministic
  begin return
    6371 * 2 * ASIN (SQRT (
        lat1-abs (LAT2) * PI ()/180/2),
        2) + COS (LAT1 * PI ()/180) * COS (ABS (LAT2) *
        pi ()/180) * Power (SIN (lng1-lng2) *
        pi ()/180/2), 2));
End

--returns the "distance in kilometers", assuming a earth radius of 6,371 km.

Summary

The above mathematical theory, I do not delve into, but also refer to the relevant information. Always feel this way to achieve a good rub.