adv, the data are provided by
adp[["v"]], adp[["a"]], and adp[["q"]]. As a
convenience, the last two of these can be accessed as numeric (as opposed to
raw) values by e.g. adp[["a", "numeric"]]. The vectors are accessed
in a similar way, e.g. adp[["heading"]], etc. Quantities in the
metadata slot are also available by name, e.g.
adp[["velocityResolution"]], etc.Assigning values. This follows the standard form, e.g. to increase
all velocity data by 1 cm/s, use adp[["v"]] <- 0.01 + adp[["v"]].
Overview of contents The show method (e.g.
show(d)) displays information about an ADP object named d.
adp devices, owing partly to the flexibility that manufacturers
provide in the setup. Prudent users will undertake many tests before trusting
the details of the data. Are mean currents in the expected direction, and of
the expected magnitude, based on other observations or physical constraints?
Is the phasing of currents as expected? If the signals are suspect, could an
incorrect scale account for it? Could the transformation matrix be incorrect?
Might the data have exceeded the maximum value, and then ``wrapped around'' to
smaller values? Time spent on building confidence in data quality is seldom
time wasted.2. Teledyne-RDI, 2012. VmDas User's Guide, Ver. 1.46.5.
metadata slot contains various
items relating to the dataset, including source file name, sampling rate,
velocity resolution, velocity maximum value, and so on. Some of these are
particular to particular instrument types, and prudent researchers will take
a moment to examine the whole contents of the metadata, either in summary
form (with str(adp[["metadata"]])) or in detail (with
adp[["metadata"]]). Perhaps the most useful general properties are
adp[["bin1Distance"]] (the distance, in metres, from the sensor to
the bottom of the first bin), adp[["cellSize"]] (the cell height, in
metres, in the vertical direction, not along the beam), and
adp[["beamAngle"]] (the angle, in degrees, between beams and an
imaginary centre line that bisects all beam pairs).The diagram provided below indicates the coordinate-axis and beam-numbering conventions for three- and four-beam ADP devices, viewed as though the reader were looking towards the beams being emitted from the transducers.
adp[["beamAngle"]] equal to 20 degrees, adp[["bin1Distance"]]
equal to 2m, and adp[["cellSize"]] equal to 1m. In the diagram, the
viewer is in the plane containing two beams that are not shown, so the two
visible beams are separated by 40 degrees. Circles indicate the centres of
the range-gated bins within the beams. The lines enclosing those circles
indicate the coverage of beams that spread plus and minus 2.5 degrees from
their centreline.
Note that adp[["oceCoordinate"]] stores the present coordinate system
of the object, and it has possible values "beam", "xyz" or
"enu". (This should not be confused with
adp[["originalCoordinate"]], which stores the coordinate system used
in the original data file.)
The data slot holds some standardized items, and
many that vary from instrument to instrument. One standard item is
adp[["v"]], a three-dimensional numeric matrix of velocities in
m/s. In this matrix, the first index indicates time, the second bin
number, and the third beam number. The meanings of the beams depends on
whether the object is in beam coordinates, frame coordinates, or earth
coordinates.
Corresponding to the velocity matrix are two matrices of type raw, and
identical dimension, accessed by adp[["a"]] and adp[["q"]],
holding measures of signal strength and data quality quality,
respectively. (The exact meanings of these depend on the particular type
of instrument, and it is assumed that users will be familiar enough with
instruments to know both the meanings and their practical consequences in
terms of data-quality assessment, etc.)
In addition to the matrices, there are time-based vectors. The vector
adp[["time"]] (of length equal to the first index of
adp[["v"]], etc.) holds times of observation. Depending on type of
instrument and its configuration, there may also be corresponding vectors
for sound speed (adp[["soundSpeed"]]), pressure
(adp[["pressure"]]), temperature (adp[["temperature"]]),
heading (adp[["heading"]]) pitch (adp[["pitch"]]), and roll
(adp[["roll"]]), depending on the setup of the instrument.
The precise meanings of the data items depend on the instrument type. All
instruments have v (for velocity), q (for a measure of data
quality) and a (for a measure of backscatter amplitude, also called
echo intensity).
Teledyne-RDI profilers have an additional item g (for
percent-good).
VmDas-equiped Teledyne-RDI profilers additional navigation data, with
details listed in the table below; note that the RDI documentation [2] and
the RDI gui use inconsistent names for most items.
avgSpeed Avg Speed Speed/Avg/Mag
avgMagnitudeVelocityEast Avg Mag Vel East ?
avgMagnitudeVelocityNorth Avg Mag Vel North ?
avgTrackMagnetic Avg Track Magnetic Speed/Avg/Dir (?)
avgTrackTrue Avg Track True Speed/Avg/Dir (?)
avgTrueVelocityEast Avg True Vel East ?
avgTrueVelocityNorth Avg True Vel North ?
directionMadeGood Direction Made Good Speed/Made Good/Dir
firstLatitude First latitude Start Lat
firstLongitude First longitude Start Lon
firstTime UTC Time of last fix End Time
lastLatitude Last latitude End Lat
lastLongitude Last longitude End Lon
lastTime UTC Time of last fix End Time
numberOfHeadingSamplesAveraged Number heading samples averaged ?
numberOfMagneticTrackSamplesAveraged Number of magnetic track samples averaged ?
numberOfPitchRollSamplesAvg Number of magnetic track samples averaged ?
numberOfSpeedSamplesAveraged Number of speed samples averaged ?
numberOfTrueTrackSamplesAvg Number of true track samples averaged ?
primaryFlags Primary Flags ?
shipHeading Heading ?
shipPitch Pitch ?
shipRoll Roll ?
speedMadeGood Speed Made Good Speed/Made Good/Mag
speedMadeGoodEast Speed MG East ?
speedMadeGoodNorth Speed MG North ?
}
For Teledyne-RDI profilers, there are four three-dimensional arrays
holding beamwise data. In these, the first index indicates time, the
second bin number, and the third beam number (or coordinate number, for
data in xyz, enu or other coordinate systems). In
the list below, the quoted phrases are quantities as defined in Figure 9
of reference 1.
vis ``velocity'' in m/s, inferred from two-byte signed
integer values (multiplied by the scale factor that is stored invelocityScalein the metadata).qis ``correlation magnitude'' a one-byte quantity stored
as typerawin the object. The values may range from 0 to 255.ais ``backscatter amplitude``, also known as ``echo
intensity'' a one-byte quantity stored as typerawin the object.
The values may range from 0 to 255.gis ``percent good'' a one-byte quantity stored asrawin the object. The values may range from 0 to 100.Finally, there is a vector adp[["distance"]] that indicates the bin
distances from the sensor, measured in metres along an imaginary centre
line bisecting beam pairs. The length of this vector equals
dim(adp[["v"]])[2].
The processingLog slot is in standard form and needs little comment.
read.oce will usually read the data. If not, one may use the
general ADP function read.adp or specialized variants
read.adp.rdi, read.adp.nortek or
read.adp.sontek or read.adp.sontek.serial.ADP data may be plotted with plot.adp function, which is a
generic function so it may be called simply as plot.
Statistical summaries of ADP data are provided by the generic function
summary, while briefer overviews are provided with show.
Conversion from beam to xyz coordinates may be done with
beamToXyzAdp, and from xyz to enu (east north up) may be done
with xyzToEnuAdp. toEnuAdp may be used to
transfer either beam or xyz to enu. Enu may be converted to other coordinates
(e.g. aligned with a coastline) with enuToOtherAdp.