Lookup tables magnetic declinations

It is generally accepted by the CLIWOC team that the wind directions, reported by the ships’ officers, were relative to the magnetic North direction. Navigators were well aware of the difference between the true and magnetic north direction, but the compasses (we assumed that the bearing-compasses were mostly used for determining the wind direction) were not always adjusted. Therefore the wind direction has to be corrected. In the following table the magnetic declination (or variation, as it is known on board ships) is given for the whole CLIWOC period (1750-1850) for every 5x5 degree square. To find the correction, look it up with a rounded (to 5 whole degrees) position and the year of observation. The found number has to be added to the wind direction.

Table name: MagneticDeclination

Field name

Description

Lat Latitude in decimal degrees; North is positive, South is negative
Lon Longitude in decimal degrees; East is positive, West is negative
Year Year
Declination Declination in degrees