开发LBS应用之根据一点的经纬度实现附近点的查询 - geohash

叁歲伎倆 2022-08-07 09:55 141阅读 0赞

# 开发LBS应用之 根据一点的经纬度实现附近点的查询 - geohash #

时间 2014-07-31 15:13:13  [segmentfault-博客 ][segmentfault-_] *原文*  [ http://blog.segmentfault.com/cloudmario/1190000000624088][http_blog.segmentfault.com_cloudmario_1190000000624088]

## geohash ##

这年头和LBS相关的应用越来越火. 从最早的foursquare的热闹程度就可见一般, 现在就更不用说微信、陌陌了 (什么, 没听过... 哥们, 你out 了). 和LBS有关的应用一般都包括一些共同的操作, 最常见的一个, 就是找附近的东东（餐馆, 商店, 妞....）. 所以, 这里就抛出了一个问题, 怎样才能在大量经纬度数据中检索出附近的点呢?

geohash能做到:

*  [https://github.com/CloudSide/geohash][https_github.com_CloudSide_geohash]
 *  [https://github.com/lyokato/objc-geohash][https_github.com_lyokato_objc-geohash]
 *  例如: 假设我的数据库里存储着1亿条包含经纬度的用户数据，用iPhone/android手机定位得到 新浪总部(理想国际大厦)的经纬度: 39.98123848, 116.30683690 然后去数据库查找附近的妞 ![m6vY73.gif][]

require_once('geohash.class.php'); $geohash = new Geohash; //得到这点的hash值 $hash = $geohash->encode(39.98123848, 116.30683690); //取前缀，前缀约长范围越小 $prefix = substr($hash, 0, 6); //取出相邻八个区域 $neighbors = $geohash->neighbors($prefix); array_push($neighbors, $prefix); print_r($neighbors);

*  得到9个geohash值

//得到9个geohash值 Array ( [top] => wx4eqx [bottom] => wx4eqt [right] => wx4eqy [left] => wx4eqq [topleft] => wx4eqr [topright] => wx4eqz [bottomright] => wx4eqv [bottomleft] => wx4eqm [0] => wx4eqw )

*  范围如图:

![j6VnayV.png][]

*  用sql语句查询

SELECT * FROM xy WHERE geohash LIKE 'wx4eqw%'; SELECT * FROM xy WHERE geohash LIKE 'wx4eqx%'; SELECT * FROM xy WHERE geohash LIKE 'wx4eqt%'; SELECT * FROM xy WHERE geohash LIKE 'wx4eqy%'; SELECT * FROM xy WHERE geohash LIKE 'wx4eqq%'; SELECT * FROM xy WHERE geohash LIKE 'wx4eqr%'; SELECT * FROM xy WHERE geohash LIKE 'wx4eqz%'; SELECT * FROM xy WHERE geohash LIKE 'wx4eqv%'; SELECT * FROM xy WHERE geohash LIKE 'wx4eqm%';

*  看一下是否用上索引 (一共有50多万行测试数据):

索引:

![YnEFfaM.png][]

数据:

![uiQvU3m.png][]

*  看一下查询是否够高效?：

EXPLAIN SELECT * FROM xy WHERE geohash LIKE 'wx4eqw%';

![jMbeqm.png][]

恩, HOHO!!

其他资料：

\- geohash演示: [ http://openlocation.org/geohash/geohash-js/][http_openlocation.org_geohash_geohash-js]

\- wiki: [ http://en.wikipedia.org/wiki/Geohash][http_en.wikipedia.org_wiki_Geohash]

\- 原理: [ https://github.com/CloudSide/geohash/wiki][https_github.com_CloudSide_geohash_wiki]

[segmentfault-_]: http://www.tuicool.com/sites/3uEjYv
[http_blog.segmentfault.com_cloudmario_1190000000624088]: http://blog.segmentfault.com/cloudmario/1190000000624088?utm_source=tuicool
[https_github.com_CloudSide_geohash]: https://github.com/CloudSide/geohash
[https_github.com_lyokato_objc-geohash]: https://github.com/lyokato/objc-geohash
[m6vY73.gif]: /images/20220805/1900f6d5d6054fabb2539f01fd6e5c3e.png
[j6VnayV.png]: /images/20220805/c6b42de20841427fab00f1f0bf6aaea5.png
[YnEFfaM.png]: /images/20220805/dc759cb48dc548ebb51b02c5199388f7.png
[uiQvU3m.png]: /images/20220805/0760fe46244b4be7b9f8c06590430b5c.png
[jMbeqm.png]: /images/20220805/f7c47c51ac214dc59004e095a59decd4.png
[http_openlocation.org_geohash_geohash-js]: http://openlocation.org/geohash/geohash-js/
[http_en.wikipedia.org_wiki_Geohash]: http://en.wikipedia.org/wiki/Geohash
[https_github.com_CloudSide_geohash_wiki]: https://github.com/CloudSide/geohash/wiki