agonic การใช้

• Magnetic declination has been measured in many countries, including the U . S . The line of zero declination ( the " agonic line " ) in North America runs from the North Magnetic Pole through Lake Superior and southward into the Gulf of Mexico.
• By convention, declination is positive when magnetic north is east of true north, and negative when it is to the west . " Isogonic lines " are lines on the Earth's surface along which the declination has the same constant value, and lines along which the declination is zero are called " agonic lines ".