ROS package for detecting gazebo actors from above?

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Hello,

I am trying to assemble a simulation in gazebo to mimic a search and rescue mission using drones. For this, I am placing some gazebo actors in the world and I want to use a drone with a camera facing downwards to detect those actors. I already manged to get the drones working in gazebo, and placing the actors. Now I need to do the image processing part, I saw that there are already some packages that detect persons such as http://wiki.ros.org/Robots/TIAGo/Tuto... and http://wiki.ros.org/opencv_apps. However, I want to be able to detect those actors from above.

Are there any packages that can detect persons with images from above? Are there any packages that can be trained to detect different objects?