Declination refers to the angle between true north and magnetic north. The line drawn through points with the same declination is known as isogonic line.

Explanation:
- Isogonic lines are imaginary lines drawn on a map or chart connecting points of equal magnetic declination.
- Magnetic declination is the angle between true north (geographic north) and magnetic north, and it varies from place to place on the Earth's surface.
- The Earth's magnetic field is not uniform, and the magnetic poles do not coincide with the geographic poles. Therefore, a compass needle does not point directly towards true north in most places.
- Isogonic lines help represent the spatial distribution of magnetic declination. These lines connect locations where the angle of declination is the same.
- Isogonic lines are typically shown on maps and charts in order to assist with navigation and to correct compass readings.
- The lines are often curved and can be seen as contours on a map, similar to lines of equal elevation.
- The isogonic lines change over time due to the movement of the Earth's magnetic field, so maps and charts need to be updated regularly to reflect the most accurate information.
- The line drawn through points with zero declination is known as the agonic line. This line represents the locations where the compass needle points directly towards true north.
- The line drawn through points with the same magnetic field strength is known as an isodynamic line.
- Gnomic lines, on the other hand, are not related to declination. They are a type of map projection that shows great circles as straight lines.

In conclusion, the line drawn through points of the same declination is called isogonic line. It helps visualize the distribution of magnetic declination on maps and charts.