Current-measuring instruments that infer flow direction using magnetic
compasses require a correction for magnetic declination, in order to infer
currents with x and y oriented eastward and northward, respectively.
applyMagneticDeclination() is a generic function that handles this task by
altering velocity components (and heading values, if they exist). It works
for objects of the cm, adp and adv and cm
classes by calling
applyMagneticDeclination(object = "oce", declination = "ANY", debug = "ANY")
an object of cm, adp, or adv class.
numeric value holding magnetic declination in degrees, positive for clockwise from north.
an integer specifying whether debugging information is
to be printed during the processing. This is a general parameter that
is used by many
The returned value is a copy of
object that has been modified in 4 ways.
(1) the horizontal components of velocity are rotated clockwise by
declination degrees. (2) If the object holds heading values, then
declination is added to them. (3) The
north item in the
is set to
"geographic", and a warning is issued if this was also the value
object. (4) The
declination item in the
metadata slot is set to
the value supplied to this function.
an object of the same class as
object, modified as described
Dan Kelley, aided, for the adp and adv variants, by Clark Richards and Jaimie Harbin.
magneticField() to determine the declination,
inclination and intensity at a given spot on the world, at a given time.
Other things related to magnetism:
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