系统环境：Ubuntu18.04.6 LTS
1.Loam的安装前要求：
1.1 ROS安装：参考我的另一篇博客
Ubuntu18.04安装ROS-melodic保姆级教程_灬杨三岁灬的博客-CSDN博客还是那句话，有时候加了这行也不好使，我是疯狂试了20+次，最后打了一局游戏，回来就过了，这就得看网络看命了，不行就在网上搜搜终极大招（动手能力差的不建议）。有时候加了这行也不好使，我是疯狂试了10+次，出现3.3之后就能用了，这就得看网络看命了，不行就在网上搜搜终极大招（动手能力差的不建议）。多试几十次，不行几百次，换手机网络也是，多试几次，这东西很玄学，不一定哪次就过了。多试几十次，不行几百次，换手机网络也是，多试几次，这东西很玄学，不一定哪次就过了。1.1.设置sources.list。https://blog.csdn.net/qq_23473839/article/details/131719477
1.2 PCL安装：
Ubuntu18.04安装PCL保姆级教程_灬杨三岁灬的博客-CSDN博客Ubuntu18.04安装PCL保姆级教程https://blog.csdn.net/qq_23473839/article/details/132128455?csdn_share_tail=%7B%22type%22%3A%22blog%22%2C%22rType%22%3A%22article%22%2C%22rId%22%3A%22132128455%22%2C%22source%22%3A%22qq_23473839%22%7D
2.安装：
2.1.建立catkin工作空间（我取名为catkin_loam_velodyne）
2.2.建立src文件夹
2.3.编译
cd ~/catkin_loam_velodyne/src/
git clone https://github.com/laboshinl/loam_velodyne.git
cd ~/catkin_loam_velodyne
catkin_make -DCMAKE_BUILD_TYPE=Release 3.编译出现的问题：
3.1.找不到pcl_conversions：
CMake Error at /opt/ros/melodic/share/catkin/cmake/catkinConfig.cmake:83 (find_package):
Could not find a package configuration file provided by "pcl_conversions"
with any of the following names:
pcl_conversionsConfig.cmake
pcl_conversions-config.cmake
Add the installation prefix of "pcl_conversions" to CMAKE_PREFIX_PATH or
set "pcl_conversions_DIR" to a directory containing one of the above files.
If "pcl_conversions" provides a separate development package or SDK, be
sure it has been installed.
Call Stack (most recent call first):
loam_velodyne/CMakeLists.txt:4 (find_package)
原因：缺少某些库
解决办法：
sudo apt-get install libvtk6-jni
sudo apt-get install libvtk6-java
sudo apt-get install libvtk6-dev
sudo apt-get install libvtk6-qt-dev
sudo apt-get install libpcl-dev
sudo apt-get install ros-melodic-pcl-conversions
sudo apt-get install ros-melodic-pcl-ros
sudo apt-get install ros-melodic-navigation以下代码只针对Ubuntu18.04对应的ROS melodic版本，其余版本可将代码中melodic自行替换为相应的版本。
4.运行Loam：
Shell1：
source ~/catkin_slam/catkin_loam_velodyne/devel/setup.bash
roslaunch loam_velodyne loam_velodyne.launchShell2：（跑Loam的数据集）
rosbag play ~/Dataset/A-LOAM/nsh_indoor_outdoor.bag结果：
5.运行出现的问题：
5.1.找不到package路径：
ERROR: cannot launch node of type [loam_velodyne/multiScanRegistration]: Cannot locate node of type [multiScanRegistration] in package [loam_velodyne]. Make sure file exists in package path and permission is set to executable (chmod +x)
ERROR: cannot launch node of type [loam_velodyne/laserOdometry]: Cannot locate node of type [laserOdometry] in package [loam_velodyne]. Make sure file exists in package path and permission is set to executable (chmod +x)
ERROR: cannot launch node of type [loam_velodyne/laserMapping]: Cannot locate node of type [laserMapping] in package [loam_velodyne]. Make sure file exists in package path and permission is set to executable (chmod +x)
ERROR: cannot launch node of type [loam_velodyne/transformMaintenance]: Cannot locate node of type [transformMaintenance] in package [loam_velodyne]. Make sure file exists in package path and permission is set to executable (chmod +x)
原因：编译的时候devel/lib没生成对应文件
解决办法：删除build和devel文件夹，重新编译即可
5.2.线程down掉
[multiScanRegistration-2] process has died [pid 5419, exit code -11, cmd /home/shuhang/catkin_slam/catkin_loam_velodyne/devel/lib/loam_velodyne/multiScanRegistration /multi_scan_points:=/velodyne_points __name:=multiScanRegistration __log:=/home/shuhang/.ros/log/8ec97a84-24a3-11ee-a67c-49f24c8dffb1/multiScanRegistration-2.log].
log file: /home/shuhang/.ros/log/8ec97a84-24a3-11ee-a67c-49f24c8dffb1/multiScanRegistration-2*.log
原因：本人后来重装Ubuntu就暂时没有这个问题了，怀疑是PCL版本不匹配的问题
解决办法：卸载PCL并重装
第一次装Loam的时候各种问题，装PCL的时候也是各种问题。重装Ubuntu后安装PCL极其顺利，Loam也极其顺利。如果Loam编译和运行很艰难，多半是PCL的问题。
