🔍 Key Concepts

• Magnetic variation: the angle between true north and magnetic north • Difference between isogonic and agonic lines on an isomagnetic chart • How lines of equal magnetic variation are labeled on charts

💭 Think About

• Which term is used for lines joining places of equal magnetic variation that is NOT zero? • What special name is given to the line where magnetic variation is exactly zero? • Look at the roots of the words: what does the prefix "a-" usually mean in scientific terms?

✅ Before You Answer

• Be sure you know that isogonic lines connect equal (non-zero) variation values • Identify which option specifically refers to zero magnetic variation rather than just any variation • Confirm that the term you choose is the standard one used on navigation and isomagnetic charts