Merge pull request laboshinl#106 from naoki-mizuno/update-readme

Update README

README.md

@@ -1,3 +1,5 @@
+# loam_velodyne
+
 ![Screenshot](/capture.bmp)
 Sample map built from [nsh_indoor_outdoor.bag](http://www.frc.ri.cmu.edu/~jizhang03/Datasets/nsh_indoor_outdoor.bag) (opened with [ccViewer](http://www.danielgm.net/cc/))
 
@@ -7,7 +9,7 @@ All sources were taken from [ROS documentation](http://docs.ros.org/indigo/api/l
 
 Ask questions [here](https://github.com/laboshinl/loam_velodyne/issues/3).
 
-How to build with catkin:
+## How to build with catkin
 
 ```
 $ cd ~/catkin_ws/src/
@@ -17,21 +19,35 @@ $ catkin_make -DCMAKE_BUILD_TYPE=Release
 $ source ~/catkin_ws/devel/setup.bash
 ```
 
-Running:
+## Running
+
 ```
 roslaunch loam_velodyne loam_velodyne.launch
 ```
 
-In second terminal play sample velodyne data from [VLP16 rosbag](https://db.tt/t2r39mjZ):
+In second terminal play sample velodyne data from [VLP16 rosbag](http://www.frc.ri.cmu.edu/~jizhang03/Datasets/):
 ```
 rosbag play ~/Downloads/velodyne.bag 
 ```
 
 Or read from velodyne [VLP16 sample pcap](https://midas3.kitware.com/midas/folder/12979):
 ```
-roslaunch velodyne_pointcloud VLP16_points.launch pcap:="/home/laboshinl/Downloads/velodyne.pcap"
+roslaunch velodyne_pointcloud VLP16_points.launch pcap:="$HOME/Downloads/velodyne.pcap"
 ```
 
+## Troubleshooting
+
+### `multiScanRegistration` crashes right after playing bag file
+
+Issues [#71](https://github.com/laboshinl/loam_velodyne/issues/71) and
+[#7](https://github.com/laboshinl/loam_velodyne/issues/7) address this
+problem. The current known solution is to build the same version of PCL that
+you have on your system from source, and set the `CMAKE_PREFIX_PATH`
+accordingly so that catkin can find it. See [this
+issue](https://github.com/laboshinl/loam_velodyne/issues/71#issuecomment-416024816)
+for more details.
+
+
 ---
 [Quantifying Aerial LiDAR Accuracy of LOAM for Civil Engineering Applications.](https://ceen.et.byu.edu/sites/default/files/snrprojects/wolfe_derek.pdf) Derek Anthony Wolfe