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Special oceanographic demands, processing and distribution
Oceanographers can use RS data at three moments:
- before an expedition for planning,
- during an expedition to be sure to be.at the right spot,
- after an expedition, to "fill in the gaps" between their
point or line measurements.
"Before" and "after", means using retrospective data; "during the
expedition" means using either an on-board receiving system or
information given from land-based receiving stations by telephone,
fac-simile or telex.
Since the contrasts sought are sometimes very small, care should
be taken in the processing to preserve these small differences
and to be able to reproduce them in the format required.
Concerning formats, it is also important to keep in mind that one
of the activities of oceanographers is to compare data from
different areas and from different time periods. The format of RS
data should be as such as to maintain a constant quality over a
iong period of time and should be compatible with formats from
other sources.
Before retrospective data can be ordered, the oceanographer needs
a good and cheap quick-look to see whether the phenomenae he is
looking.for, are actually present in that.image.
The first experience
Imagery from Landsat, Skylab and other US platforms
indication of the potential of RS for oceanography.
Landsat data can be very useful, if the appropriate enhancement
can be made. In the Netherlands, a small project is under way to
investigate whether it is possible to find a standard enhancement
for Landsat data over the Southern North Sea.
The optical sensors seem to detect chlorophyll, sediments and
pollution. Infrared sensors give the distribution of the Sea
Surface Temperature (SST).
SEASAT gave a tremendous amount of data, in spite of its short
lifetime of 100 days. Still much of the data is not analysed.
data indicated the possibility of obtaining data on waves,
currents and winds by the use of microwave techniques. The
Synthetic Aperture Radar showed interesting but largely yet
unexplained patterns over the sea.
gave a first
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The present
For the oceanographers today two alternatives exist, besides
Landsat:
- the experimental NIMBUS-7 with the Coastal Zone Color Scanner,
a multispectral scanner intended to analyse the color of the
sea to obtain chlorophyll,sediment and yellow outstance content.
It took one year after the launch to get the first CZCS data to
the oceanographers. Much of the data is yet unanalyzed, partly
because of the lack of appropriate processing algorithms for
Specific sea areas. CZCS data of Europe is split over three
archives at this moment of which the contents are not all known.
- The operational meteorological satellites, producing visible and
infrared data. This data is available through most meteorolo-
gical offices. The enhancements, necessary to make the data
useful for oceanography, are applied only in a few cases.
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