在ubuntu20.04上装ros并运行vins-fusion遇到了许多问题，踩了很多坑，总结一下发在这里。ROS Noetic 和ceres-solver、eigen等库的安装就略过了。在git了 vins-fusion后直接编译会出现各种报错，这是由于noetic的opencv4头文件和参数名与vins-fusion所使用的opencv3不同造成的，使用两种方式解决这个问题。

1.使用非ROS Noetic自带OPENCV编译工程

修改Vins-Fusion工程头文件及部分参数

第一步是改掉代码中这些地方，总结如下

由于ubuntu20.04所支持Ros Noetic 自带opencv4 与vins-fusion所依赖的opencv3冲突
做出修改
1.camera_model 头文件中 Chessboard.h添加
#include <opencv2/imgproc/types_c.h>
#include <opencv2/calib3d/balib3d_c.h>

2.CameraCalibration.h添加
#include <opencv2/imgproc/types_c.h>
#include <opencv2/imgproc/imgproc_c.h>

3.loop_fusion/src/VRIEF.h添加
#include <opencv2/imgproc/types_c.h>

4.loop_fusion/src/pose_graph.cpp
* 修改 CV_FONT_HERSHEY_SIMPLEX -> cv::FONT_HERSHEY_SIMPLEX

5. vins_estimator/src/feature_tracker.h 添加
#include <opencv2/highgui.hpp>
#include <opencv2/cvconfig.h>
#include <opencv2/imgproc/types_c.h>

6. vins_estimator/src/KITTIOdomTest.cpp KITTIGPSTest.cpp
* 修改 CV_LOAD_IMAGE_GRAYSCALE -> cv::IMREAD_GRAYSCALE

完成以上几步就可以初步编译vins-fusion工程成功了。我在读取传感器配置步骤遇到了Segmentation Fault（core dump）的问题，即

#在一个终端上，运行正常
cd catkin_ws
source ./devel/setup.bash
roslaunch vins vins_rviz.launch //这一步是正常的

#在第二个终端上，这一步出现了Segmentation Fault（core dump）的问题，导致可视化读不到数据
cd catkin_ws
source ./devel/setup.bash
rosrun vins vins_node ~/catkin_ws/src/VINS-Fusion/config/euroc/euroc_mono_imu_config.yaml

#在第三个终端上，运行正常
cd catkin_ws
source ./devel/setup.bash
rosbag play YOUR_DATASET_FOLDER/MH_01_easy.bag

#这一步与第二步一样，出现Segmentation Fault（core dump）的问题
(optional) rosrun loop_fusion loop_fusion_node ~/catkin_ws/src/VINS-Fusion/config/euroc/euroc_stereo_imu_config.yaml

出现这个问题的原因是，opencv4和opencv3版本不同导致，这需要使用OPENCV3进行工程的编译

使用非ROS Noetic自带OPENCV版本编译工程

感谢 链接1 链接2 链接3解决了这个问题，主要是修改cv_bridge的配置，使vins-fusion工程链接到opencv3库上
首先找到cv_bridge配置文件所在位置

cd /opt/ros/noetic/share/cv_bridge/cmake
sudo gedit cv_bridgeConfig.cmake

在90行左右，修改如下内容
将

if(NOT "include;/usr/include/opencv4 " STREQUAL " ")
  set(cv_bridge_INCLUDE_DIRS "")
  set(_include_dirs "include;/usr/include/opencv4")

改为

if(NOT "include;(/usr/local/include/opencv2) " STREQUAL " " )
  set(cv_brideg_INCLUDE_DIRS "")
  set(_include_dirs "include;(/usr/local/include/opencv2)") #()括号部分是你的OPENCV3的安装路径

之后将指定库文件也修改为自己安装的opencv库文件，这一步需要手动添加。
将

set(libraries "cv_bridge;/usr/lib/x86_64-linux-gnu/libopencv_calib3d.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_dnn.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_features2d.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_flann.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_highgui.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_ml.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_objdetect.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_photo.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_stitching.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_video.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_videoio.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_aruco.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_bgsegm.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_bioinspired.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_ccalib.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_datasets.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_dnn_objdetect.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_dnn_superres.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_dpm.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_face.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_freetype.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_fuzzy.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_hdf.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_hfs.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_img_hash.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_line_descriptor.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_optflow.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_phase_unwrapping.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_plot.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_quality.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_reg.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_rgbd.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_saliency.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_shape.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_stereo.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_structured_light.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_superres.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_surface_matching.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_text.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_tracking.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_videostab.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_viz.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_ximgproc.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_xobjdetect.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_xphoto.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_core.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_imgproc.so.4.2.0;/usr/lib/x86_64-linux-gnu/libopencv_imgcodecs.so.4.2.0")

改为,其实就是你/usr/local/lib/路径里所有libopencv开头的文件，这是我的，你们可以拿去抄抄哈哈哈。

set(libraries "cv_bridge;/usr/local/lib/libopencv_calib3d.so;/usr/local/lib/libopencv_features2d.so.3.4.16;/usr/local/lib/libopencv_imgproc.so.3.4;/usr/local/lib/libopencv_shape.so;/usr/local/lib/libopencv_videoio.so.3.4.16;/usr/local/lib/libopencv_calib3d.so.3.4;/usr/local/lib/libopencv_flann.so;/usr/local/lib/libopencv_imgproc.so.3.4.16;/usr/local/lib/libopencv_shape.so.3.4;/usr/local/lib/libopencv_video.so;/usr/local/lib/libopencv_calib3d.so.3.4.16;/usr/local/lib/libopencv_flann.so.3.4;/usr/local/lib/libopencv_ml.so;/usr/local/lib/libopencv_shape.so.3.4.16;/usr/local/lib/libopencv_video.so.3.4;/usr/local/lib/libopencv_core.so;/usr/local/lib/libopencv_flann.so.3.4.16;/usr/local/lib/libopencv_ml.so.3.4;/usr/local/lib/libopencv_stitching.so;/usr/local/lib/libopencv_video.so.3.4.16;/usr/local/lib/libopencv_core.so.3.4;/usr/local/lib/libopencv_highgui.so;/usr/local/lib/libopencv_ml.so.3.4.16;/usr/local/lib/libopencv_stitching.so.3.4;/usr/local/lib/libopencv_videostab.so;/usr/local/lib/libopencv_core.so.3.4.16;/usr/local/lib/libopencv_highgui.so.3.4;/usr/local/lib/libopencv_objdetect.so;/usr/local/lib/libopencv_stitching.so.3.4.16;/usr/local/lib/libopencv_videostab.so.3.4;/usr/local/lib/libopencv_dnn.so;/usr/local/lib/libopencv_highgui.so.3.4.16;/usr/local/lib/libopencv_objdetect.so.3.4;/usr/local/lib/libopencv_superres.so;/usr/local/lib/libopencv_videostab.so.3.4.16;/usr/local/lib/libopencv_dnn.so.3.4;/usr/local/lib/libopencv_imgcodecs.so;/usr/local/lib/libopencv_objdetect.so.3.4.16;/usr/local/lib/libopencv_superres.so.3.4;/usr/local/lib/libopencv_viz.so;/usr/local/lib/libopencv_dnn.so;/usr/local/lib/libopencv_dnn.so.3.4.16;/usr/local/lib/libopencv_imgcodecs.so.3.4;/usr/local/lib/libopencv_photo.so;/usr/local/lib/libopencv_superres.so.3.4.16;/usr/local/lib/libopencv_viz.so.3.4;/usr/local/lib/libopencv_features2d.so;/usr/local/lib/libopencv_imgcodecs.so.3.4.16;/usr/local/lib/libopencv_photo.so.3.4;/usr/local/lib/libopencv_videoio.so;/usr/local/lib/libopencv_viz.so.3.4.16")

修改完就可以正常运行vins-fusion了

2.使用Docker

第二种方法就是使用docker，20.04很好装docker，需要注意的的是，如果是非root用户的话，要先将用户加入docker group，即sudo usermod -aG docker 你的用户名然后再重启(原文写的登出再登入我试了没用，重启才行)，我把Dokcerfile里的ceres-solver的git链接从google改到了github然后去外边看看就可以了，之后也可以正常运行vins-fusion。