R: Alter a cm Object to Account for Magnetic Declination

applyMagneticDeclination,cm-method {oce}

R Documentation

Alter a cm Object to Account for Magnetic Declination

Description

Current-meter (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”).

Usage

## S4 method for signature 'cm'
applyMagneticDeclination(
  object = "oce",
  declination = 0,
  debug = getOption("oceDebug")
)

Arguments

`object`	a cm object.
`declination`	numeric value holding magnetic declination in degrees, positive for clockwise from north.
`debug`	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.

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.

Value

A cm object, adjusted as outlined in “Details”.

Author(s)

Dan Kelley