For example, the annual variation value of Beijing area is c =-3' 56 ".
The magnetic declination in 1 9 6 4 was 517' 23 ",and after 3 9 years, it was 2 0 0 3;
á = A + n c = 5。 2 9 - 3 9 * 0 .0 6 5 = 2 .7 6
That is, the north-south direction is 2.76 degrees west than the direction indicated by the south needle.
When we measure the direction with a compass, if we don't calculate the magnetic deflection angle, there is no way to find the real north-south direction. In geomantic omen, there is a saying that "gold divides into one line, wealth does not meet each other", which shows the importance of using a compass to determine the direction. Therefore, before going to various places to investigate geomantic omen, it is necessary to calculate the local magnetic deflectometer, and then adjust the pointer of the compass to the upper surface of the magnetic declination for use. If not, it's a tiny difference, a thousand miles away. Be careful, be careful.
Table: Annual variation values of longitude, latitude and magnetic declination in major cities of China;
northern latitude
east longitude
Annual variation value
The reference value is 1964.
Shanghai
3 1 1 1′
12 1 26′
-3′57″
West 3 53'18 "
Nanjing
32 04′
1 18 47′
-3′45″
3 43' 03 "W.
Hangzhou
30 15′
120 10′
-3′45″
West 3 5 1' 30 "
Changsha
28 12′
1 12 56′
-3′00″
1 54' 00 "west
Chongqing
29 32′
106 34′
-2′30″
West longitude130' 00 "
Chengdu
30 40′
104 05′
-2′20″
1 15' 00 "west
Fuzhou
26 05′
1 17 18′
-3′20″
2 04 ft W.
Guangzhou
23 15′
1 13 18′
-2′45″
0.52 ft 30 in W.
Kunming
25 04′
102 44′
-2′00″
0 56' 00 "W.
Beijing
39 55′
1 16 27′
-3′56″
W longitude 5 17' 23 "
Tianjin
39 08′
1 16 12′
-3′55″
5 feet 23 inches 30 inches west longitude
Qingdao
36 04′
120 19′
-4′02″
West 5 15' 00 "
Xi'an
34 15′
108 56′
-3′00″
West 2 14' 00 "
Urumqi
44 46′
87 34′
+2′05″
2 53' 24 "W.
Lhasa
28 40′
9 1 05′
- 1′ 15″
0 42' 30 "W.
Magnetic declination of major cities in China
Chengdu 1 degree 16 cent west
Chongqing 1 34 minutes west
Guilin west longitude 1 degree 22 points
Nanjing west longitude 4 degrees 03 minutes
Kunming 1 degree 00 minutes west
Lhasa 0 degree 2 1 minute west
Mohe 1 1 00' (West)
Xuchang 3 40 ft (west)
Urumqi 2 44 ft (west)
Qiqihar 9 54' (West)
Tianjin 5: 30 (West)
Yinchuan 2 35 ft (west)
Harbin 9: 39 (West)
Jinan 5 0 1' (West)
Xi' An 2 29' (West)
Changchun 8: 53 (West)
Hohhot 4 36' (West)
Lanzhou 1 44' (West)
Manzhouli 8 40' (West)
Zhou Xu 4 27 ft (west)
Xining 1 22' (West)
Shenyang 7 44' (West)
Taiyuan 4 1 1' (West)
Lhasa 0 2 1' (West)
Dalian 6 35 ft (west)
Baotou 4 03' (West)
Beijing 5 degrees 50 minutes (West)
Zhengzhou 3 50 feet (west)