This class stores G1SST model-satellite products.
dataAs with all oce objects, the data slot
for g1sst objects is a
list containing the main data for the object.
metadataAs with all oce objects, the metadata slot
for g1sst objects is a list containing
information about the data or about the object itself.
processingLogAs with all oce objects, the processingLog slot
for g1sst 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 g1sst objects (see [[<-,g1sst-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 g1sst
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 [[,g1sst-method
operator, as e.g. o[["data"]] and o[["metadata"]], respectively.
The [[,g1sst-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
G1SST is an acronym for global 1-km sea surface temperature, a product
that combines satellite data with the model output. It is provided by
the JPO ROMS (Regional Ocean Modelling System) modelling group.
See the JPL website (reference 1) to learn more about the data, and see
the read.g1sst() documentation for an example
of downloading and plotting.
It is important not to regard G1SST data in the same category as,
say, amsr data, because the two products
differ greatly with respect to cloud cover. The satellite used by
amsr has the ability to sense water temperature
even if there is cloud cover, whereas g1sst fills in cloud
gaps with model simulations. It can be helpful to consult
reference 1 for a given time, clicking and then unclicking the radio button
that turns off the model-based filling of cloud gaps.
JPO OurOcean Portal https://ourocean.jpl.nasa.gov/SST/
(link worked in 2016 but was seen to fail 2017 Feb 2).
Other classes holding satellite data:
amsr-class,
landsat-class,
satellite-class
Other things related to g1sst data:
[[,g1sst-method,
[[<-,g1sst-method,
read.g1sst()