🔍 Key Concepts

• Pilot charts often show both the magnetic variation and how it changes over time. • Lines of equal magnetic variation are called isogonic lines. • The annual rate of change must be tied directly to the variation value so a navigator can update it for the present year.

💭 Think About

• On what feature of the chart would it be most logical to print the amount the variation changes each year? • If you needed to quickly apply the yearly change to a given variation value at your position, where would you look so you don’t have to scan the whole chart? • Which option specifically connects the rate of change to the value of variation at a particular place?

✅ Before You Answer

• Identify where the lines of equal magnetic variation are on a pilot chart and how they’re labeled. • Check which choice explicitly links the annual rate of change to those variation lines, rather than using a separate color or inset. • Confirm that the method would allow a navigator to easily update the variation from the chart’s reference year to the current year.