按照官方教程安装cartographer的时候：

wstool merge -t src https://raw.githubusercontent.com/googlecartographer/cartographer_ros/master/cartographer_ros.rosinstall

报错：

ERROR in config: Unable to download URL [https://raw.githubusercontent.com/googlecartographer/cartographer_ros/master/cartographer_ros.rosinstall]: <urlopen error [Errno 104] Connection reset by peer>

因为github访问总是不稳定…

先观察一下这个文件是什么 ，在浏览器中打开该网址发现如下

- git: {local-name: cartographer, uri: 'https://github.com/cartographer-project/cartographer.git', version: 'master'}
- git: {local-name: cartographer_ros, uri: 'https://github.com/cartographer-project/cartographer_ros.git', version: 'master'}

应该就是 .rosinstall 文件规定了需要clone的功能包，所以我们只需要在当前工作空间的src中的.rosinstall 文件中加入如上内容，然后跳过开头的merge指令就行了。