American practical navigator: an epitome of navigation and nautical astronomy (1914)
Bowditch, Nathaniel, 1773-1838, United States. Navy Dept. Bureau of Equipment, Logan, George Wood, 1868-1915 · Washington, Govt. Print. Off. · leaf 54
Fig. 12. 48 THE COMPASS EKROR. E is approximately equal to the mean of the deviations on North and South; orto the mean of those on East and West with sign reversed; or to the mean of thosemeans. In the example, E is equal to ^ (-15° 29 + 17° 52)=+1° 11; or toi ( + 9°06-9°56)=-0°25; or to-| ( + 1°…
Navigation · Nautical astronomy
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