Also, having no corners, this protractor can measure shorter journey legs, which means no more fumbling with additional rulers, leading to inaccurate flight planning. The reciprocal headings are printed in blue for quick calculations. Our pilots have used the round protractor and found it to be easier and more accurate to use than the standard square protractor. Constructed in clear perspex and measuring only 110mm diameter, the new round protractor is a must for any pilot striving for accuracy.