Need position estimate in compass-less operation

I want to use GPS to control the yaw of the arducopter instead of using compasses. I use marvelmind super beacon for the indoor positioning system. After disabling compasses and enabling GSF, I cannot arm the drone due to “Need position Estimate”. What could be the reason and how to solve it. I use a pixhawk 2.4.8 and the firmware version is arducopter 4.1.5

It is not getting a valid position estimate from the marvelmind and/or compass.

Try enabling the gsf filter

Thank you for your reply. I have already enabled the gsf filter by setting [EK3_SRC1_YAW] = 8 (GSF). But I still encounter the same problem.