def get_estimator(self):
        """return the configured estimator as string from initial parameters"""

        mav_type = self._ulog.initial_parameters.get('MAV_TYPE', None)
        if mav_type == 1: # fixed wing always uses EKF2
            return 'EKF2'

        mc_est_group = self._ulog.initial_parameters.get('SYS_MC_EST_GROUP', None)
        return {0: 'INAV',
                1: 'LPE',
                2: 'EKF2',
                3: 'IEKF'}.get(mc_est_group, 'unknown ({})'.format(mc_est_group))
return the configured estimator as string from initial parameters