EKF: Simplify calculation of height above terrain observation variance
EKF: Simplify calculation of height above terrain observation variance

The tilt compensation being applied previously was based on a flat earth geometric model assuming perfect tilt knowledge which reduces the effect of range errors on height error as the vehicle tilts. however in the real world, variations in terrain gradient and uncertainty in vehicle tilt and sensor alignment tend to increase height error with tilt, so the adjustment of observation variance with tilt has been removed given we do not have a valid mathematical model on which to base it.

PX4/ecl,PX4/ecl,PX4/ecl,PX4/ecl,PX4/ecl