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 ".