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APPENDIX IX. Magnetic variation
magnetic variation


In the UK, the current magnetic variation can be estimated by assuming (in 2000) a value of 2º 37' W on the Greenwich Meridian at 50º N, and then allowing an increase of 15' for each degree of latitude northwards and one of 27' for each degree of longitude westward. The annual change at present is about 12' decrease.

Historical values of the magnetic variation for London (Greenwich from 1900) are given in the following table:

Year

Magnetic variation

1580

11º 15' E

1622

5º 56' E

1665

1º 22' W

1730

13º 00' W

1773

21º 09' W

1850

22º 24' W

1900

16º 29' W

1925

13º 10' W

1950

9º 07' W

1975

6º 39' W

1998

3º 32' W