Erle Copter in indoor environment project

Hello :slight_smile: ,

So I want to fly the Elre Copter in indoor room and I have some questions:
1- since the GPS is disabled in indoor environment, which modes can I use to takeoff and land autonomously and fly the UAV in a specific Hight?? do you have examples or codes??

2- can I connect four of these IR receiver to the Erle Brain 2.0 and analyse the data from them (analyse the signal width)?? where can I connect these 4 receivers in Erle Brain??

3- Based on the signal received in the IR receivers, the drone will follow the strongest signal (Infrared tracking system) is that possible to do with the Erle Brain 2.0??

4- for obstacles avoidance can you suggest a cheap Ultrasonic and if you have its code ??

I really appreciate your kind help

Regards :slight_smile: