Update Readme.md

Readme.md

@@ -15,3 +15,15 @@ This simulation is based on [OpenUAV](https://github.com/Open-UAV) project.
 5. `source setup-install.sh` (press <kbd>Return</kbd> to continue when asked)
 6. When it finishes, type `make posix_sitl_default`
 7. Then try to run Gazebo by typing `gazebo` in your terminal
+
+# FAQ #
+<details>
+ <summary>If after making `posix_sitl`, Gazebo doesn’t launch and gives you a error message regarding `geographiclib`</summary>
+ <p>Do the following:
+In your terminal type:  sudo apt-get install ros-kinetic-mavros ros-kinetic-mavros-extras
+When that installation is ready type: 
+cd; wget https://raw.githubusercontent.com/mavlink/mavros/master/mavros/scripts/install_geographiclib_datasets.sh
+./install_geographiclib_datasets.sh 
+you might have to make the install_geographiclib_datasets.sh executable.
+In terminal(home): sudo ./install_geographiclib_datasets.sh</p>
+</details>