Update 4 3 horizontal vector field

4-3-horizontal-vector-field.md

@@ -19,6 +19,8 @@ _Rendering Pane_ will immediately display the vector field of wind, and a new la
 
 ##### 3. Explore wind flow at different altitudes (if any).
 
+If your dataset includes wind flow data at multiple altitude, you can select a particular height level, or easily change to the next/previous height level.
+
 On _Horizontal Plane_ menu category of _Menu Bar_, you will find _Vertical Level_ drop-down control, where you can select height level among all the levels available in your dataset. You can also click _Move Up / Move Down_ button in order to increase / decrease the selected level.
 
 ##### 4. Change the settings for color mapping (optional).