Cannot set EKF origin position on ardurover (but on arducopter it works)

I want to setup noGPS with ORB SLAM for my ground vehicle.
At the time I`m trying to control vehicle position via VISION_POSITION_ESTIMATE.
AHRS_EKF_TYPE = 3
EK3_ENABLE = 1
EK3_SRC1_POSXY = 6
EK3_SRC1_VELXY = 6 (and EK3_SRC1_VELXY = 3)
VISO_TYPE = 1

On ArduCopter with that parameters i can set EKF origin position, but on ArduRover I can`t. Why?