R: Class to Store XBT Data

xbt-class {oce} | R Documentation

## Class to Store XBT Data

### Description

This class stores expendable bathythermograph (XBT) data, e.g. from a Sippican device. Reference 1 gives some information on Sippican devices, and reference 2 is a useful introduction to the modern literature on XBTs in general.

### Slots

`data`

  As with all `oce` objects, the `data` slot for `xbt` objects is a list containing the main data for the object. The key items stored in this slot are `depth` (or `z`) and `temperature`, although some datasets also have `soundSpeed`. Note that `depth` and `z` are inferred from time in water, using an empirical formula for instrument descent rate, and that `soundSpeed` is #' calculated using a fixed practical salinity of 35. Note that the `[[` accessor will compute any of `depth`, `z` or `pressure`, based on whatever is in the data object. Similarly, `soundspeed` will compute sound speed (assuming a practical salinity of 35), if that that item is present in the `data` slot.

`metadata`

  As with all `oce` objects, the `metadata` slot for `xbt` objects is a list containing information about the `data` or about the object itself.

`processingLog`

  As with all `oce` objects, the `processingLog` slot for `xbt` objects is a list with entries describing the creation and evolution of the object. The contents are updated by various `oce` functions to keep a record of processing steps. Object summaries and `processingLogShow()` both display the log.

### Modifying slot contents

Although the `[[<-` operator may permit modification of the contents of xbt objects (see `[[<-,xbt-method`), it is better to use `oceSetData()` and `oceSetMetadata()`, because those functions save an entry in the `processingLog` that describes the change.

### Retrieving slot contents

The full contents of the `data` and `metadata` slots of a xbt object may be retrieved in the standard R way using `slot()`. For example `slot(o,"data")` returns the `data` slot of an object named `o`, and similarly `slot(o,"metadata")` returns the `metadata` slot.

The slots may also be obtained with the `[[,xbt-method` operator, as e.g. `o[["data"]]` and `o[["metadata"]]`, respectively.

The `[[,xbt-method` operator can also be used to retrieve items from within the `data` and `metadata` slots. For example, `o[["temperature"]]` can be used to retrieve temperature from an object containing that quantity. The rule is that a named quantity is sought first within the object's `metadata` slot, with the `data` slot being checked only if `metadata` does not contain the item. This `[[` method can also be used to get certain derived quantities, if the object contains sufficient information to calculate them. For example, an object that holds (practical) salinity, temperature and pressure, along with longitude and latitude, has sufficient information to compute Absolute Salinity, and so `o[["SA"]]` will yield the calculated Absolute Salinity.

It is also possible to find items more directly, using `oceGetData()` and `oceGetMetadata()`, but neither of these functions can retrieve derived items.

### Author(s)

Dan Kelley

### References

1. Sippican, Inc. "Bathythermograph Data Acquisition System: Installation, Operation and Maintenance Manual (P/N 308195, Rev. A)," 2003. https://pages.uoregon.edu/drt/MGL0910_Science_Report/attachments/MK21_ISA_Manual_Rev_A.pdf.

2. Cheng, Lijing, John Abraham, Gustavo Goni, Timothy Boyer, Susan Wijffels, Rebecca Cowley, Viktor Gouretski, et al. "XBT Science: Assessment of Instrumental Biases and Errors." Bulletin of the American Meteorological Society 97, no. 6 (June 2016): 924-33. https://doi.org/10.1175/BAMS-D-15-00031.1.

### See Also

Other things related to xbt data: `[[,xbt-method`, `[[<-,xbt-method`, `as.xbt()`, `plot,xbt-method`, `read.xbt.noaa1()`, `read.xbt()`, `subset,xbt-method`, `summary,xbt-method`, `xbt.edf`, `xbt`

Other classes provided by oce: `adp-class`, `adv-class`, `argo-class`, `bremen-class`, `cm-class`, `coastline-class`, `ctd-class`, `lisst-class`, `lobo-class`, `met-class`, `oce-class`, `odf-class`, `rsk-class`, `sealevel-class`, `section-class`, `topo-class`, `windrose-class`

[Package oce version 1.2-0 Index]