Plus you usually have to move a bit. GPS tells you which direction you are moving, not which direction you are facing. Usually it becomes valid when the GPS speed becomes valid too.The signal was weak. I was indoor.
Once you do have a reasonably good directional fix, you could use the gyroscopes to keep ahold of that... except that gyroscopes don't seem to be common on Android phones. Phones that support VR should have them, Samsung seems to be good in that regard.magnetometers will get you most of the way there
Usually it becomes valid when the GPS speed becomes valid too.
https://racelogic.support/01VBOX_Automotive/01General_Information/Knowledge_Base/How_Does_GPS_Work?Doppler is not related. It calculates the speed and bearing based on the changes in the position.
Well, that makes me a winner (I think) because I learned two things today:I've learned something today.