You are flying on a heading of 355°T at a true airspeed of 110 knots. Your GPS unit tells you that you have a track made good (actual track over the ground) of 010°T and a groundspeed of 125 knots. What is the wind velocity?
1 Set the airspeed under the airspeed dot (110kts)
2 Put the heading (355°) under the index by rotating the compass rose
3 Since our heading is 355° and track is 010°, the drift is 15° to starboard (right). Mark along the line that represents 15° starboard drift on the navigational computer.
If it helps, you can draw a small diagram of the heading & track to make sure you get the drift correct.
4 Mark the groundspeed (125kts) across your drift mark.
5 Slide the airspeed dot down to the top of the wind grid. Rotate the compass rose until the cross you marked is vertically down from the airspeed dot.
Read the wind direction from under the index and the wind speed from your cross mark:
The wind is 247/34
(wind from 247° at 37 knots)
Make sure to check for any large errors. Check that the wind you calculated makes sense – if you are drifting right the wind should be from the left, and if you are drifting left the wind should be from the right.