Project - Quadcopter Moving Autonomously

Hello guys , I want to improve myself and knowledge in Autonomous navigation.
So I am preparing to start a project , which is a quadcopter that moves to a certain coordinates that I pre-locate.

For example I want it to go to a certain place , at a certain height and to overcome obstacles , and moves to a certain latitude and longitude.

So I need some sensors , as Pressure sensor ( for height ) , GPS ( for position ) , ultrasonic sensor ( for obstacles ) .

Now what I want is , how to start , any ideas ?

Thank you guys , I appreciate any comment

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