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.
dataAs 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.
metadataAs with all oce objects, the metadata slot
for xbt objects is a list containing
information about the data or about the object itself.
processingLogAs 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.
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.
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.
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.
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.
10.1175/BAMS-D-15-00031.1
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