Agonic Lines are lines indicated where there is no magnetic declination.

Agonic Lines are lines indicated where there is no magnetic declination.

• A. Are lines indicating areas with the same magnetic declination.
• B. Are lines showing the boundaries of time zones.
• C. Are lines indicated where there is no magnetic declination.
• D. Are lines used to measure wind direction.

Answer: (C)

Magnetic declination is the angular difference between true north and magnetic north. An agonic line is the place where this difference is zero, so the compass points exactly at true north with no correction needed. That’s why this statement is best: along an agonic line there is no magnetic declination to account for. Other lines describe different ideas: lines of equal declination (isogonic lines) show where the declination is the same but not necessarily zero; time zone boundaries are a civil geography concept with no relation to magnetism; lines used to measure wind direction pertain to meteorology, not magnetic navigation.

Magnetic declination is the angular difference between true north and magnetic north. An agonic line is the place where this difference is zero, so the compass points exactly at true north with no correction needed. That’s why this statement is best: along an agonic line there is no magnetic declination to account for.

Other lines describe different ideas: lines of equal declination (isogonic lines) show where the declination is the same but not necessarily zero; time zone boundaries are a civil geography concept with no relation to magnetism; lines used to measure wind direction pertain to meteorology, not magnetic navigation.