Is the magnetic declination decreasing in the west or increasing in the east? As far as I know, it should be that the west decreases and the east increases, but there is such a sentence in the magnetic declination of Baidu Encyclopedia: My understanding is that most areas of China are west-biased. In the case of west-biased, the north pointed by the magnetic needle is the left side of true north. Take the Forbidden City in Beijing as an example. From the map, the central axis of the Forbidden City is about 5 to the left, and the magnetic declination of Beijing is 6 (to the west). This phenomenon can be understood as the fact that the central axis of the Forbidden City is determined by the magnetic north (it is purely coincidental to check the information). For example, standing in Tiananmen Square and measuring the central axis of the Forbidden City with a compass, the azimuth of magnetic north is 0, and the azimuth of true north is 354.