manual: fix velodyne manual in en and cn

modules/drivers/velodyne/README.md

-## Overview
 
-Velodyne_ is a collection of ROS_ packages supporting `Velodyne high
-definition 3D LIDARs`_.
+## Velodyne
+velodyne driver runs as nodelet, including:
+1. data packet processing --> /sensor_velodyne64_driver
+2. point cloud generation --> /sensor_velodyne64_convert
+3. compensation --> /sensor_velodyne64_compensator
+ 
+Compensation relies on `tf` to query the coordination transform, so gnss_driver is required to run the velodyne nodelets.
+ 
+### Topics
+* /apollo/sensor/velodyne64/VelodyneScanUnified --> velodyne_msgs/VelodyneScanUnified
+* /apollo/sensor/velodyne64/PointCloud2 --> sensor_msgs/PointCloud2
+* /apollo/sensor/velodyne64/compensator/PointCloud2 --> sensor_msgs/PointCloud2
+ 
+### Coordination
+* world
+* novatel
+* velodyne64
+ 
+### Build Velodyne
 
+```bash 
+# in dev docker
+cd /apollo
+bash apollo.sh buildvelodyne
+```
+The output will overwrite the velodyne driver in `/apollo/bazel-apollo/external/ros/`.
+ 
+### Configure Velodyne Driver
+First, specify the parameters of the car.
+
+**velodyne model and running mode**
+```xml
+<!-- 64E_S3D_STRONGEST|64E_S3D_LATEST |64E_S3D_DUAL -->
+<arg name="model" default="64E_S3D_STRONGEST"/>
+```
+ 
+**online intrinsic extraction**
+```xml
+<arg name="calibration_online" default="true" />
+```
+When calibration_online is true, intrinsic parameter file is not needed, otherwise, please specify the intrinsic parameter file as below:
+
+**intrinsic parameter file**
+```xml
+<arg name="velodyne64_calibration_file" default="$(find velodyne_pointcloud)/params/64E_S3_calibration_example.yaml"/>
+```
+ 
+**extrinsic parameter file**
+```xml
+<arg name="extrinsics_velodyne64" default="$(find velodyne_pointcloud)/params/velodyne64_novatel_extrinsics_example.yaml"/>
+```
 
-### HOW TO RUN
+**timezone** 
+```xml
+<!-- Beijing UTC+8 -->
+<!-- California UTC-8 -->
+<arg name="time_zone" default="-8" />
+```
+### Start Velodyne Driver
+**Plese first change the parameters in the launch file for your car**
 ```bash
 roslaunch velodyne start_velodyne.launch
+# or
+bash /apollo/scripts/velodyne.sh
+```
+ 
+### Export pcd
+**Plese first change the parameters in the launch file for your car**
+Default export directory: /apollo/data/pcd
+```bash
+roslaunch velodyne export_pcd.launch
 ```
-motion compensator depends tf2, so gnss_deriver should avaliable too.
\ No newline at end of file
+ 
+### velodyne Data Validation
+```bash
+roslaunch velodyne velodyne_check.launch
+```
+In directory `/apollo/data/log/`, two files are generated by velodyne driver: `velodyne_hz.yyyy-mm-dd-HH-MM-SS.log` and `velodyne_hz.yyyy-mm-dd-HH-MM-SS.log.err` The `.log` file records the time interval and frequency between each frame of compensated point cloud. The `.log.err` file reocrds the timestamp and time interval of the point cloud whose frequency is lower than 9Hz.
+
+### FAQ
+1. velodyne port 2368 poll() timeout
+	The network between the host and velodyne is having problem. Please use `sudo tcpdump -i eth0 udp port 2368` to check if velodyne packets are received.
+2. cannot find transform ...
+	`Compensaton` relies on `tf`, please double check if `gnss_driver` has been started, and also use `rostopic echo /tf` to check if there are any message in the tf.
+ 

modules/drivers/velodyne/README_cn.md

 
 ## velodyne
-velodyne驱动是以nodelet的形式实现的，包含了
+velodyne驱动是以nodelet的形式实现的，包含了:
+
 1. 数据读取打包 --> /sensor_velodyne64_driver
 2. 生成点云 --> /sensor_velodyne64_convert
 3. 运动补偿 --> /sensor_velodyne64_compensator
  
-三个部分的处理节点，其中`运动补偿`需要依赖`tf`来进行坐标转换查询，因此需要和`gnss_driver`一起运行才能正常工作
+三个处理节点，其中`运动补偿`需要依赖`tf`来进行坐标转换查询，因此需要和`gnss_driver`一起运行才能正常工作
  
 ### Topics
+
 * /apollo/sensor/velodyne64/VelodyneScanUnified --> velodyne_msgs/VelodyneScanUnified
 * /apollo/sensor/velodyne64/PointCloud2 --> sensor_msgs/PointCloud2
 * /apollo/sensor/velodyne64/compensator/PointCloud2 --> sensor_msgs/PointCloud2
  
 ### 坐标系
+
 * world
 * novatel
 * velodyne64
@@ -27,6 +30,7 @@ bash apollo.sh buildvelodyne
 产出会覆盖`/apollo/bazel-apollo/external/ros/`中原有的velodyne驱动相关文件
  
 ### 配置velodyne驱动
+
 首先要指定每个车的对应参数
 
 **velodyne型号与工作模式**
@@ -39,13 +43,14 @@ bash apollo.sh buildvelodyne
 ```xml
 <arg name="calibration_online" default="true" />
 ```
+
 当该参数设置为`true`的时候，不需要提供内参文件；设置为`false`时，必须提供内参文件
-**内参**
+**内参文件**
 ```xml
 <arg name="velodyne64_calibration_file" default="$(find velodyne_pointcloud)/params/64E_S3_calibration_example.yaml"/>
 ```
  
-**外参**
+**外参文件**
 ```xml
 <arg name="extrinsics_velodyne64" default="$(find velodyne_pointcloud)/params/velodyne64_novatel_extrinsics_example.yaml"/>
 ```