adp-class {oce} | R Documentation

## Class to Hold adp (adcp) Data

### Description

This class stores data from acoustic Doppler profilers. Some manufacturers call these ADCPs, while others call them ADPs; here the shorter form is used by analogy to ADVs.

### Details

The `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.

The bin geometry of a four-beam profiler is illustrated below, for `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.

Oce name | RDI doc name | RDI GUI name
`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.

- `v` is “velocity” in m/s, inferred from two-byte signed integer values (multiplied by the scale factor that is stored in `velocityScale` in the metadata).

- `q` is “correlation magnitude” a one-byte quantity stored as type `raw` in the object. The values may range from 0 to 255.

- `a` is “backscatter amplitude“, also known as “echo intensity” a one-byte quantity stored as type `raw` in the object. The values may range from 0 to 255.

- `g` is “percent good” a one-byte quantity stored as `raw` in 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.

### methods

Extracting values Matrix data may be accessed as illustrated above, e.g. or an adp object named `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`.

### Dealing with suspect data

There are many possibilities for confusion with `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.

### References

1. Teledyne-RDI, 2007. WorkHorse commands and output data format. P/N 957-6156-00 (November 2007).

2. Teledyne-RDI, 2012. VmDas User's Guide, Ver. 1.46.5.

### See Also

A file containing ADP data is usually recognized by Oce, and so `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`.

[Package oce version 0.9-18 Index]