编译之前检查依赖：
rosdep check --from-path src --ignore-src -r -y
rosdep install --from-path src --ignore-src -r -y
编译fast-lio-sam：
错误1：
CMake Error at FAST_LIO_SAM/CMakeLists.txt:61 (find_package):
By not providing "FindGeographicLib.cmake" in CMAKE_MODULE_PATH this
project has asked CMake to find a package configuration file provided by
"GeographicLib", but CMake did not find one.
Could not find a package configuration file provided by "GeographicLib"
with any of the following names:
GeographicLibConfig.cmake
geographiclib-config.cmake
Add the installation prefix of "GeographicLib" to CMAKE_PREFIX_PATH or set
"GeographicLib_DIR" to a directory containing one of the above files. If
"GeographicLib" provides a separate development package or SDK, be sure it
has been installed.
-- Configuring incomplete, errors occurred!
See also "/home/tx/fast_lio_sam_ws/build/CMakeFiles/CMakeOutput.log".
See also "/home/tx/fast_lio_sam_ws/build/CMakeFiles/CMakeError.log".
Invoking "cmake" failed
解决方法：
sudo apt install libgeographic-dev
然后在Cmakelists.txt里面修改以下
set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "/usr/share/cmake/geographiclib/")
find_package (GeographicLib REQUIRED)
错误2：
usr/local/include/gtsam/base/Vector.h:75:52: error: static assertion failed: Error: GTSAM was built against a different version of Eigen
75 | GTSAM_EIGEN_VERSION_WORLD==EIGEN_WORLD_VERSION &&
原因是GTSAM自带的eigen和我系统安装的eigen之间有冲突。GTSAM编译的时候默认使用了自带的eigen，而系统中如果还手动安装过一个eigen的话，就会出现两个eigen的冲突。
解决方法（跟版本也有关系，4.0.3可以用这种，4.1.0不管用）：
在CMakeLists.txt文件中添加：
set(GTSAM_USE_SYSTEM_EIGEN ON)
错误3：
[laserMapping-1] process has died [pid 186915, exit code 127, cmd /home/dlab/lesson8/fastlio_slam_ws/devel/lib/fast_lio_sam/fastlio_sam_mapping __name:=laserMapping __log:=/home/dlab/.ros/log/accb0f1a-8809-11ee-a2f5-f35b7aca3fd2/laserMapping-1.log].
log file: /home/dlab/.ros/log/accb0f1a-8809-11ee-a2f5-f35b7aca3fd2/laserMapping-1*.log
原因：
libmetis-gtsam.so这个文件位于路径"/usr/local/lib" 中，而程序默认找的位置是路径"/usr/lib"，所以没有找到，看了很多方法，还挺麻烦的，所以自己想出来一种方法------把文件复制过去
解决方法：
sudo cp /usr/local/lib/libmetis-gtsam.so /usr/lib/