SITL-With-Gazebo.md

+Reference: https://raw.githubusercontent.com/Texas-Aerial-Robotics/Controls-ROS/master/README.md
+
+## Install Gazebo
+
+Setup your computer to accept software from http://packages.osrfoundation.org:
+```
+sudo sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu-stable `lsb_release -cs` main" > /etc/apt/sources.list.d/gazebo-stable.list'
+```
+
+Setup keys:
+```
+wget http://packages.osrfoundation.org/gazebo.key -O - | sudo apt-key add -
+```
+
+Reload software list:
+```
+sudo apt update
+```
+
+Install Gazebo:
+```
+sudo apt install gazebo9 libgazebo9-dev
+```
+
+Install ROS plugins:
+```
+sudo apt install ros-melodic-gazebo-ros ros-melodic-gazebo-plugins
+```
+
+Get Gazebo plugin for APM (ArduPilot Master):
+```
+cd ~
+git clone https://github.com/SwiftGust/ardupilot_gazebo
+cd ardupilot_gazebo
+git checkout gazebo9
+mkdir build
+cd build
+cmake ..
+make -j4
+sudo make install
+```
+
+Set paths for models:
+```
+echo 'export GAZEBO_MODEL_PATH=~/ardupilot_gazebo/gazebo_models' >> ~/.bashrc
+. ~/.bashrc
+```
+
+Add Gazebo Models:
+```
+hg clone https://bitbucket.org/osrf/gazebo_models ~/gazebo_ws/gazebo_models
+cd ~/gazebo_ws/gazebo_models
+echo 'export GAZEBO_MODEL_PATH=~/gazebo_ws/gazebo_models' >> ~/.bashrc
+source ~/.bashrc
+```
+
+## 8. Run Simulator With Gazebo
+
+In one Terminal (Terminal 1), run SITL:
+```
+cd ~/ardupilot/ArduCopter/
+sim_vehicle.py -j4 -f Gazebo --console
+```
+
+In another Terminal (Terminal 2), run Gazebo:
+```
+gazebo --verbose ~/ardupilot_gazebo/gazebo_worlds/iris_irlock_demo.world
+```
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