This class stores echosounder data. Echosounder objects may be
read with read.echosounder(),
summarized with summary,echosounder-method(),
and plotted with plot,echosounder-method().
The findBottom()
function infers the ocean bottom from tracing the strongest reflector from
ping to ping.
dataAs with all oce objects, the data slot
for echosounder objects is a
list containing the main data for the object.
metadataAs with all oce objects, the metadata slot
for echosounder objects is a list containing
information about the data or about the object itself.
processingLogAs with all oce objects, the processingLog slot
for echosounder 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 echosounder objects (see [[<-,echosounder-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 echosounder
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 [[,echosounder-method
operator, as e.g. o[["data"]] and o[["metadata"]], respectively.
The [[,echosounder-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.
Dan Kelley
An infrequently updated record of the instrument position, in
timeSlow, longitudeSlow and latitudeSlow. These are
used in plotting maps with plot,echosounder-method().
An interpolated record of the instrument position, in time,
longitude, and latitude. Linear interpolation is used to
infer the longitude and latitude from the variables listed above.
depth, vector of depths of echo samples (measured positive
downwards in the water column). This is calculated from the inter-sample
time interval and the sound speed provided as the soundSpeed argument
to read.echosounder(), so altering the value of the latter will
alter the echosounder plots provided by plot,echosounder-method().
The echosounder signal amplitude a, a matrix whose number of
rows matches the length of time, etc., and number of columns equal to
the length of depth. Thus, for example, a[100,] represents
the depth-dependent amplitude at the time of the 100th ping.
A matrix named b exists for dual-beam and split-beam cases.
For dual-beam data, this is the wide-beam data, whereas a is the
narrow-beam data. For split-beam data, this is the x-angle data.
A matrix named c exists for split-beam data, containing the
y-angle data.
In addition to these matrices, ad-hoc calculated matrices named
Sv and TS may be accessed as explained in the next section.
Other things related to echosounder data:
[[,echosounder-method,
[[<-,echosounder-method,
as.echosounder(),
echosounder,
findBottom(),
plot,echosounder-method,
read.echosounder(),
subset,echosounder-method,
summary,echosounder-method