Update README.md

Added documentation for stereo ROS node and EuRoC dataset example.

README.md

@@ -139,6 +139,7 @@ This will create **libORB_SLAM.so**  at *lib* folder and the executables **mono_
 
 #7. ROS Examples
 
+### Building the nodes for mono, stereo and RGB-D
 1. Add the path including *Examples/ROS/ORB_SLAM2* to the ROS_PACKAGE_PATH environment variable. Open .bashrc file and add at the end the following line. Replace PATH by the folder where you cloned ORB_SLAM2:
 
   ```
@@ -153,13 +154,38 @@ This will create **libORB_SLAM.so**  at *lib* folder and the executables **mono_
   cmake .. -DROS_BUILD_TYPE=Release
   make -j
   ```
-3. For a monocular input from topic `/camera/image_raw` run node ORB_SLAM2/Mono. You will need to provide the vocabulary file and a settings file. See the monocular examples above.
+
+### Running Monocular Node
+For a monocular input from topic `/camera/image_raw` run node ORB_SLAM2/Mono. You will need to provide the vocabulary file and a settings file. See the monocular examples above.
 
   ```
   rosrun ORB_SLAM2 Mono PATH_TO_VOCABULARY PATH_TO_SETTINGS_FILE
   ```
+
+### Running Stereo Node
+For a stereo input from topic `/camera/left/image_raw` and `/camera/right/image_raw` run node ORB_SLAM2/Stereo. You will need to provide the vocabulary file and a settings file. If you **provide rectification matrices** (see Examples/Stereo/EuRoC.yaml example), the node will recitify the images online, **otherwise images must be pre-rectified**.
+
+  ```
+  rosrun ORB_SLAM2 Stereo PATH_TO_VOCABULARY PATH_TO_SETTINGS_FILE ONLINE_RECTIFICATION
+  ```
+
+**Example**: Download a rosbag (e.g. V1_01_easy.bag) from the EuRoC dataset (http://projects.asl.ethz.ch/datasets/doku.php?id=kmavvisualinertialdatasets). Open 3 tabs on the terminal and run the following command at each tab:
+  ```
+  roscore
+  ```
+
+  ```
+  rosrun ORB_SLAM2 Stereo Vocabulary/ORBvoc.txt Examples/Stereo/EuRoC.yaml true
+  ```
+
+  ```
+  rosbag play --pause V1_01_easy.bag /cam0/image_raw:=/camera/left/image_raw /cam1/image_raw:=/camera/right/image_raw
+  ```
+
+Once ORB-SLAM2 has loaded the vocabulary, press space in the rosbag tab. Enjoy! (a powerful computer is requires to run the most exigent sequences of this dataset).
 
-4. For an RGB-D input from topics `/camera/rgb/image_raw` and `/camera/depth_registered/image_raw`, run node ORB_SLAM2/RGBD. You will need to provide the vocabulary file and a settings file. See the RGB-D example above.
+### Running RGB_D Node
+For an RGB-D input from topics `/camera/rgb/image_raw` and `/camera/depth_registered/image_raw`, run node ORB_SLAM2/RGBD. You will need to provide the vocabulary file and a settings file. See the RGB-D example above.
 
   ```
   rosrun ORB_SLAM2 RGBD PATH_TO_VOCABULARY PATH_TO_SETTINGS_FILE