EKF: add baro bias estimator using GNSS altitude

msg/CMakeLists.txt

@@ -44,6 +44,7 @@ set(msg_files
 	airspeed.msg
 	airspeed_validated.msg
 	airspeed_wind.msg
+	baro_bias_estimate.msg
 	battery_status.msg
 	camera_capture.msg
 	camera_trigger.msg

msg/baro_bias_estimate.msg

@@ -0,0 +1,10 @@
+uint64 timestamp                # time since system start (microseconds)
+uint64 timestamp_sample         # the timestamp of the raw data (microseconds)
+
+uint32 baro_device_id		# unique device ID for the sensor that does not change between power cycles
+float32 bias			# estimated barometric altitude bias (m)
+float32 bias_var		# estimated barometric altitude bias variance (m^2)
+
+float32 innov			# innovation of the last measurement fusion (m)
+float32 innov_var		# innovation variance of the last measurement fusion (m^2)
+float32 innov_test_ratio	# normalized innovation squared test ratio