cm) instruments determine directions from onboard compasses,
so interpreting velocity components in geographical coordinates requires that
magnetic declination be taken into account. This is what the present
function does (see “Details”).
a cm object.
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
oce functions. Generally, setting
turns off the printing, while higher values suggest that more information
be printed. If one function calls another, it usually reduces the value of
debug first, so that a user can often obtain deeper debugging
by specifying higher
A cm object, adjusted as outlined in “Details”.
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.
magneticField() to determine the declination,
inclination and intensity at a given spot on the world, at a given time.