Stream external pose message from vision system so that it can be log…

…ged (#185)

* Stream external pose message from vision system so that it can be logged

* changed name of message for improved calrity

message_definitions/v1.0/messages.xml

@@ -377,7 +377,22 @@
       <field name="exponential"         type="uint8" unit="bool">Exponential chirp active</field>
     </message>
 
-    <!-- 46 is free-->
+    <message name="EXTERNAL_POSE_DOWN" id="46">
+      <description>
+        Position, speed and orientation in local frame from a remote vision system
+      </description>
+      <field name="timestamp" type="float" unit="mus">Timestamp from the measurement</field>
+      <field name="ned_x"     type="float" unit="m">NED x position in vision frame</field>
+      <field name="ned_y"     type="float" unit="m">NED y position in vision frame</field>
+      <field name="ned_z"     type="float" unit="m">NED z position in vision frame</field>
+      <field name="ned_xd"    type="float" unit="m/s">NED x speed in vision frame</field>
+      <field name="ned_yd"    type="float" unit="m/s">NED y speed in vision frame</field>
+      <field name="ned_zd"    type="float" unit="m/s">NED z speed in vision frame</field>
+      <field name="body_qi"   type="float">Body quaternion i in NED to body</field>
+      <field name="body_qx"   type="float">Body quaternion x in NED to body</field>
+      <field name="body_qy"   type="float">Body quaternion y in NED to body</field>
+      <field name="body_qz"   type="float">Body quaternion z in NED to body</field>
+    </message>
 
     <message name="WP_MOVED_LLA" id="47">
       <field name="wp_id" type="uint8"/>