Plotting 10° Drift Lines

10° drift lines are helpful to determine how far off course you might be and useful in quickly determining headings to fly in order to regain the correct track. There is generally no need to create 10° drift markers from the departure point to the SHP, you will be quite busy during the departure and en route climb portion of the flight. Therefore, place the centre of the protractor over the SHP. The orientation of the protractor is irrelevant since we are not measuring a track just yet. Note the value that the true track line crosses (164°) then draw a line 10° to the left and right of the true track (174° and 154°). Repeat this process at the other end of the leg (destination aerodrome).