diff --git a/EKF/common.h b/EKF/common.h
index 8c4b2d7de9..a9cc104aa0 100644
--- a/EKF/common.h
+++ b/EKF/common.h
@@ -80,15 +80,6 @@ struct flow_message {
 	uint32_t dt;		///< integration time of flow samples (microseconds)
 };
 
-struct ext_vision_message {
-	Vector3f pos;	///< XYZ position in external vision's local reference frame (m) - Z must be aligned with down axis
-	Vector3f vel;	///< XYZ velocity in external vision's local reference frame (m/sec) - Z must be aligned with down axis
-	Quatf quat;		///< quaternion defining rotation from body to earth frame
-	Vector3f posVar;	///< XYZ position variances (m**2)
-	Vector3f velVar;	///< XYZ velocity variances ((m/sec)**2)
-	float angVar;		///< angular heading variance (rad**2)
-};
-
 struct outputSample {
 	Quatf  quat_nominal;	///< nominal quaternion describing vehicle attitude
 	Vector3f    vel;	///< NED velocity estimate in earth frame (m/sec)
diff --git a/EKF/estimator_interface.cpp b/EKF/estimator_interface.cpp
index 5d5e89c44a..502762c9a0 100644
--- a/EKF/estimator_interface.cpp
+++ b/EKF/estimator_interface.cpp
@@ -403,7 +403,7 @@ void EstimatorInterface::setOpticalFlowData(uint64_t time_usec, flow_message *fl
 }
 
 // set attitude and position data derived from an external vision system
-void EstimatorInterface::setExtVisionData(uint64_t time_usec, ext_vision_message *evdata)
+void EstimatorInterface::setExtVisionData(const extVisionSample& evdata)
 {
 	if (!_initialised || _ev_buffer_fail) {
 		return;
@@ -421,19 +421,13 @@ void EstimatorInterface::setExtVisionData(uint64_t time_usec, ext_vision_message
 	}
 
 	// limit data rate to prevent data being lost
-	if ((time_usec - _time_last_ext_vision) > _min_obs_interval_us) {
-		extVisionSample ev_sample_new;
+	if ((evdata.time_us - _time_last_ext_vision) > _min_obs_interval_us) {
+		_time_last_ext_vision = evdata.time_us;
+
+		extVisionSample ev_sample_new = evdata;
 		// calculate the system time-stamp for the mid point of the integration period
-		ev_sample_new.time_us = time_usec - _params.ev_delay_ms * 1000;
-
-		ev_sample_new.angVar = evdata->angVar;
-		ev_sample_new.posVar = evdata->posVar;
-		ev_sample_new.velVar = evdata->velVar;
-		ev_sample_new.quat = evdata->quat;
-		ev_sample_new.pos = evdata->pos;
-		ev_sample_new.vel = evdata->vel;
-
-		_time_last_ext_vision = time_usec;
+		ev_sample_new.time_us -= _params.ev_delay_ms * 1000;
+		ev_sample_new.time_us -= FILTER_UPDATE_PERIOD_MS * 1000 / 2;
 
 		_ext_vision_buffer.push(ev_sample_new);
 	}
diff --git a/EKF/estimator_interface.h b/EKF/estimator_interface.h
index c520e2516b..c45d725e26 100644
--- a/EKF/estimator_interface.h
+++ b/EKF/estimator_interface.h
@@ -189,7 +189,7 @@ public:
 	void setOpticalFlowData(uint64_t time_usec, flow_message *flow);
 
 	// set external vision position and attitude data
-	void setExtVisionData(uint64_t time_usec, ext_vision_message *evdata);
+	void setExtVisionData(const extVisionSample& evdata);
 
 	void setAuxVelData(const auxVelSample& auxvel_sample);
 
diff --git a/test/sensor_simulator/vio.cpp b/test/sensor_simulator/vio.cpp
index 8051c6b844..c32bca540c 100644
--- a/test/sensor_simulator/vio.cpp
+++ b/test/sensor_simulator/vio.cpp
@@ -15,10 +15,11 @@ Vio::~Vio()
 
 void Vio::send(uint64_t time)
 {
-	_ekf->setExtVisionData(time, &_vio_data);
+	_vio_data.time_us = time;
+	_ekf->setExtVisionData(_vio_data);
 }
 
-void Vio::setData(const ext_vision_message& vio_data)
+void Vio::setData(const extVisionSample& vio_data)
 {
 	_vio_data = vio_data;
 }
@@ -53,9 +54,9 @@ void Vio::setOrientation(const Quatf& quat)
 	_vio_data.quat = quat;
 }
 
-ext_vision_message Vio::dataAtRest()
+extVisionSample Vio::dataAtRest()
 {
-	ext_vision_message vio_data;
+	extVisionSample vio_data;
 	vio_data.pos = Vector3f{0.0f, 0.0f, 0.0f};;
 	vio_data.vel = Vector3f{0.0f, 0.0f, 0.0f};;
 	vio_data.quat = Quatf{1.0f, 0.0f, 0.0f, 0.0f};
diff --git a/test/sensor_simulator/vio.h b/test/sensor_simulator/vio.h
index 731dda9ffd..5b873b508a 100644
--- a/test/sensor_simulator/vio.h
+++ b/test/sensor_simulator/vio.h
@@ -50,7 +50,7 @@ public:
 	Vio(std::shared_ptr<Ekf> ekf);
 	~Vio();
 
-	void setData(const ext_vision_message& vio_data);
+	void setData(const extVisionSample& vio_data);
 	void setVelocityVariance(const Vector3f& velVar);
 	void setPositionVariance(const Vector3f& posVar);
 	void setAngularVariance(float angVar);
@@ -58,10 +58,10 @@ public:
 	void setPosition(const Vector3f& pos);
 	void setOrientation(const Quatf& quat);
 
-	ext_vision_message dataAtRest();
+	extVisionSample dataAtRest();
 
 private:
-	ext_vision_message _vio_data;
+	extVisionSample _vio_data;
 
 	void send(uint64_t time) override;