AP_NavEKF2: Add flow sensor body position offset to data buffer

libraries/AP_NavEKF2/AP_NavEKF2_Measurements.cpp

@@ -142,6 +142,8 @@ void NavEKF2_core::writeOptFlowMeas(uint8_t &rawFlowQuality, Vector2f &rawFlowRa
         // write uncorrected flow rate measurements that will be used by the focal length scale factor estimator
         // note correction for different axis and sign conventions used by the px4flow sensor
         ofDataNew.flowRadXY = - rawFlowRates; // raw (non motion compensated) optical flow angular rate about the X axis (rad/sec)
+        // write the flow sensor position in body frame
+        ofDataNew.body_offset = posOffset;
         // write flow rate measurements corrected for body rates
         ofDataNew.flowRadXYcomp.x = ofDataNew.flowRadXY.x + omegaAcrossFlowTime.x;
         ofDataNew.flowRadXYcomp.y = ofDataNew.flowRadXY.y + omegaAcrossFlowTime.y;

libraries/AP_NavEKF2/AP_NavEKF2_core.h

@@ -402,6 +402,7 @@ private:
         Vector2f    flowRadXY;      // 0..1
         Vector2f    flowRadXYcomp;  // 2..3
         uint32_t    time_ms;        // 4
+        Vector3f    body_offset;    // 5..7
     };
 
     // update the navigation filter status