I try to compile the world about UAV, I downloaded the SDF file, and I can insert this model into gazebo. When I try to compile the .world file, I add the .sdf and .config to the same file with the .world. I and the model to the world by using <uri> </uri>,however, it shows that gazebo can not find the model.
What should I do to add the model to the world?![image description](http://)(/upfiles/15049731082802547.png)(/upfiles/15049730942945814.png)