Acoustic-Doppler velocimetry instruments that infer direction using magnetic compasses need to have a correction applied for magnetic declination, if the goal is to infer currents with x and y oriented eastward and northward, respectively. This is what the present function does (see “Details”).

# S4 method for adv
  object = "oce",
  declination = 0,
  debug = getOption("oceDebug")



an adv 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 debug=0 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 debug values.


A adv 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 metadata slot is set to "geographic", and a warning is issued if this was also the value in object. (4) The declination item in the metadata slot is set to the value supplied to this function.

See also


Dan Kelley, aided by Clark Richards and Jaimie Harbin.