beamToXyzAdp(x, debug=getOption("oceDebug"))"adp".rdi data, the values at the 4th velocity
index are changed to represent the "error" velocity.) To indicate the change, the value of metadata$oce.orientation
is changed from beam to xyz.
For a 3-beam aquadopp object, the beams are transformed
into velocities using the matrix stored in the header.
For 4-beam rdi object, the beams are converted to velocity
components using formulae from section 5.5 of RD Instruments
(1998), viz. the along-beam velocity components
$B_1$,
$B_2$,
$B_3$,
and
$B_4$
are used to calculate velocity components in a cartesian
system referenced to the instrument using the following formulae:
$u=ca(B_1-B_2)$,
$v=ca(B_4-B_3)$,
$w=-b(B_1+B_2+B_3+B_4)$,
and an estimate of the error in velocity is calculated using
$e=d(B_1+B_2-B_3-B_4)$
(Note that the multiplier on $e$ is subject to discussion; RDI suggests one multiplier, but some oceanographers favour another.)
In the above,
$c=1$ if the beam geometry is convex, and
$c=-1$ if the beam geometry is concave,
$a=1/(2\sin\theta)$,
$b=1/(4\cos\theta)$
and
$d=a/\sqrt{2}$, where $\theta$
is the angle the beams make to the instrument
2. WHOI/USGS-provided Matlab code for beam-enu transformation
read.adp for other functions that relate to objects
of class "adp".