Robust aerial human detection?

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Hi guys... I am trying to detect human individuals from aerial photos, but i am having a hard time finding a smart method to make it possible. It should be robust such that all other things should be ignored, and only trigger when a human appear, how would you do that using openCV? or what method would you use. It should be able to detect people out in the sea, but at the same time ignore other things such as ships, fish and so on.