Barometer and Actual Altitude Very Different

Hello everyone,

I am a beginner PX4 user. I am using F450 frame, DJI 2212 motors and DJI phantom 3 9450 propellers. My firmware is also PX4 Developer version.

First of all, vehicle actual altitude(local position z) and barometer altitude are very different at indoor test. Vehicle has external gps but ekf primarly use barometer(I see from parameter) for estimating altitude. I know gps is not working properly. What is the reason altitude differences? Additionally, these test is to see how to fly PX4 with RC controller.

Secondly, when flying with stabilized mode,ı changed mode to altitude mode. Vehicle splash up. I think that is due to MPC_THR_HOVER parameter. What do you think about ?

You can see the two flight logs from below links.

Thanks for help.