UNDERstand 函数调用
http://www.cnblogs.com/darkknightzh/p/4994551.html
ros的navigation之———gmapping应用详解(in ros)
http://blog.youkuaiyun.com/chenxingwangzi/article/details/49802763
gmapping 分析
http://blog.youkuaiyun.com/roadseek_zw/article/details/53316177