EKF: Don't reject saturated flow data when it is the only aiding source

EKF/estimator_interface.cpp

@@ -364,20 +364,24 @@ void EstimatorInterface::setOpticalFlowData(uint64_t time_usec, flow_message *fl
 
 
 		// check magnitude is within sensor limits
+		// use this to prevent use of a saturated flow sensor when there are other aiding sources available
 		float flow_rate_magnitude;
 		bool flow_magnitude_good = true;
-
 		if (delta_time_good) {
 			flow_rate_magnitude = flow->flowdata.norm() / delta_time;
 			flow_magnitude_good = (flow_rate_magnitude <= _params.flow_rate_max);
 		}
 
+		bool relying_on_flow =  _control_status.flags.opt_flow
+				&& !_control_status.flags.gps
+				&& !_control_status.flags.ev_pos;
+
 		// check quality metric
 		bool flow_quality_good = (flow->quality >= _params.flow_qual_min);
 
 		// Always use data when on ground to allow for bad quality due to unfocussed sensors and operator handling
 		// If flow quality fails checks on ground, assume zero flow rate after body rate compensation
-		if ((delta_time_good && flow_quality_good && flow_magnitude_good) || !_control_status.flags.in_air) {
+		if ((delta_time_good && flow_quality_good && (flow_magnitude_good || relying_on_flow)) || !_control_status.flags.in_air) {
 			flowSample optflow_sample_new;
 			// calculate the system time-stamp for the mid point of the integration period
 			optflow_sample_new.time_us = time_usec - _params.flow_delay_ms * 1000 - flow->dt / 2;