Attitude estimation

Hello, II’m trying to interface Marvelmind with Pixhawk.
During my test, I found that when I plug-in Marvelmind to GPS port, then the attitude start drifting and “BAD AHRS” appears on the hud screen.
If I don’t connect Marvelmind, the compass provides a stable yaw angle and pitch and roll are well estimated by the filter.

  1. Can I use Marvelmind GPS only for postion and velocity estimation, without attitude estimation?

  2. How does the firmware determine the attitude from GPS NMEA sentences?

Thanks a lot for your support