http://blog.csdn.net/liminlu0314/article/details/8553926
http://blog.csdn.net/u011833609/article/details/18057079
http://www.cnblogs.com/LBSer/p/3298057.html
http://uohzoaix.github.io/studies/2013/05/16/geohashAlgorithm/
原文：http://www.cnblogs.com/xuxm2007/p/4207898.html