Which statement about magnetic declination is true according to the material?

• A. It changes over time and you should determine local declination before field measurements
• B. It is constant globally
• C. It is irrelevant for orientation
• D. It depends only on latitude

Answer: (A)

Magnetic declination is the angle between magnetic north (where a compass points) and geographic north (true north). It changes over time due to secular variation of Earth's magnetic field and varies by location, so you must determine the local declination for the date of your field work. This is essential for converting compass readings to true bearings, which is critical for accurate mapping and interpretation in the field. It isn’t the same everywhere, it isn’t irrelevant for orientation, and it doesn’t depend only on latitude—time and longitude (and the evolving geomagnetic field) also affect it.