Navagation using only IMU sensor

I am new to UAV navigation and I am going to use my drone indoors. So please help me understand how to force PX4 use IMU sensor and don’t use GPS

@SergeyMalashenko For indoor navigation, the UAV requires estimation of its states with high accuracy. Generally, IMU data is fused with other sensors like GPS, RangeFinder etc using state-of-the-art sensor fusion techniques to accurately estimate the states of UAV. So, IMU sensor alone is not sufficient for a stable flight and we need some sort of additional sensors.

Thank you for your reply @Yogesh_Kumar1 . But the question was about how to forcibly turn off the GPS navigation? I want to test my current device CUAV X7+ Pro in mode without GPS navigation.