Convert ADP velocity components from a beam-based coordinate system to a xyz-based coordinate system. The action depends on the type of object. Objects creating by reading RDI Teledyne, Sontek, and some Nortek instruments are handled directly.
Usage
beamToXyzAdp(x, debug = getOption("oceDebug"))Arguments
- x
an adp object.
- debug
an integer specifying whether debugging information is to be printed during the processing. This is a general parameter that is used by many
ocefunctions. Generally, settingdebug=0turns off the printing, while higher values suggest that more information be printed. If one function calls another, it usually reduces the value ofdebugfirst, so that a user can often obtain deeper debugging by specifying higherdebugvalues.
Value
An object with the first 3 velocity indices having been altered to
represent velocity components in xyz (or instrument) coordinates. (For
rdi data, the values at the 4th velocity index are changed to
represent the "error" velocity.)
To indicate the change, the value of x[["oceCoordinate"]] is
changed from beam to xyz.
Details
For a 3-beam Nortek aquadopp object, the beams are transformed into
velocities using the matrix stored in the header.
For 4-beam objects (and for the slanted 4 beams of 5-beam
objects), the along-beam velocity components \(B_1\)
\(B_2\), \(B_3\), and \(B_4\)
are converted to Cartesian velocity components \(u\)
\(v\) and \(w\)
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:
\(u=ca(B_1-B_2)\), \(v=ca(B_4-B_3)\),
\(w=-b(B_1+B_2+B_3+B_4)\). In addition to these,
an estimate of the
error in velocity is computed as
\(e=d(B_1+B_2-B_3-B_4)\).
The geometrical factors in these formulae are:
c is +1 for convex beam geometry or -1 for concave beam geometry,
\(a=1/(2\sin\theta)\)
where \(\theta\) is the angle the beams make to the axial direction
(which is available as x[["beamAngle"]]),
\(b=1/(4\cos\theta)\), and
\(d=a/\sqrt{2}\).
References
Teledyne RD Instruments. “ADCP Coordinate Transformation: Formulas and Calculations,” January 2010. P/N 951-6079-00.
WHOI/USGS-provided Matlab code for beam-enu transformation
http://woodshole.er.usgs.gov/pubs/of2005-1429/MFILES/AQDPTOOLS/beam2enu.m
See also
See read.adp() for other functions that relate to
objects of class "adp".
Other things related to adp data:
[[,adp-method,
[[<-,adp-method,
ad2cpCodeToName(),
ad2cpHeaderValue(),
adp,
adp-class,
adpAd2cpFileTrim(),
adpConvertRawToNumeric(),
adpEnsembleAverage(),
adpFlagPastBoundary(),
adpRdiFileTrim(),
adp_rdi.000,
applyMagneticDeclination,adp-method,
as.adp(),
beamName(),
beamToXyz(),
beamToXyzAdpAD2CP(),
beamToXyzAdv(),
beamUnspreadAdp(),
binmapAdp(),
enuToOther(),
enuToOtherAdp(),
handleFlags,adp-method,
is.ad2cp(),
plot,adp-method,
read.adp(),
read.adp.ad2cp(),
read.adp.nortek(),
read.adp.rdi(),
read.adp.sontek(),
read.adp.sontek.serial(),
read.aquadopp(),
read.aquadoppHR(),
read.aquadoppProfiler(),
rotateAboutZ(),
setFlags,adp-method,
subset,adp-method,
subtractBottomVelocity(),
summary,adp-method,
toEnu(),
toEnuAdp(),
velocityStatistics(),
xyzToEnu(),
xyzToEnuAdp(),
xyzToEnuAdpAD2CP()