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Proceeding of the Fist East-Europen Symposium on Advances
in Data Bases and Information Systems (ADBIS'97) St.-Petersburg, Russia,
September 2-5 1997. — St.-Pb.: St.-Petersburg University, 1997, Vol. 2,
p. 95-96
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An Integrated Data Base of Altimetric Satellite for Fundamental Geosciences Research
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This Document in Format PDF
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P.P. Medvedev, S.A. Lebedev, Yu.S. Tyupkin
- The purpose of the project is to set up an integrated
satellite altimetry data base (ISADB), which would include the results
of altimetry measurements conducted by the Russian GEOIK geodetic satellites
and by GEOSAT, ERS-1, ERS-2 and TOPEX/POSEIDON during the period starting
from 1985 until present. ISADB would also include supplementary information
necessary for the processing and interpretation of experimental data. The
software, besides ts standard DBMS functions, would also carry out the
functions of data processing and data visualization for the problem-oriented
study of the sea level changes of the world ocean and large inland basins
and for the determination of the detailed characteristics of the gravity
field of the Earth.
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The final ISADB version shall be loaded on the WWW server
of Geophysical Center and thus will be available in the Internet. We believe
that the range of application of the data base shall be sufficiently wide,
because the altimetry measurements, carried out by the GEOIK satellites,
have not been available to the wide scientific community before.
The most developed software for work with the satellite altimetry
data was realized by NASA. This software, however, allows to analyze information
measured by satellites of the same family, whereas the ISADB would allow
operation this information obtained by different satellite families. As
regards the system of express-analysis and visualization of altimeter data,
the study of the corresponding NASA methods has shown that the set of programs
realized by the participants of the project is in no part inferior to them.
The specific feature of the satellite altimetry data is that
these data take up much space and the larger part of them is resented on
the CD-ROMs. The information is recorded in the binary Hewlett-Packard
format, or VAX, as the direct-access files inverted by time (the geodetic
and exact repeat GEOSAT program), by time and satellite series (the GEOIK
experiment), by space (the intersection point bases), by exact repeat cycles
(the TOPEX/POSEIDON satellite), or by the numbers of orbital arcs (the
ERS-1 experiment).
The search and selection of data, stipulated by the developed
software, are oriented on the specific features of the structure of satellite
information. The search criterion is a logical construction based on a
single search attribute (the simple search criterion) and on the combination
of simple search criteria by the logical operations OR, AND, NOT in order
to organize the search by several attributes. Moreover, a few additional
virtual attributes of search are suggested: region, data and time, season,
cycle, the serial number of the satellite, and the orbit's number. The
attribute «region» allows to select the region of research on a real geographical
map with precision up to 0.1 sec. Since the time in the data bases is given
in seconds or the number of days and seconds from the start of the count,
the virtual «data and time» parameter, for the user's convenience, permits
to give the time of measurement in the usual terms: data, month, ear, hour,
minute and second. The attribute «season» is designated for selection of
a certain seasonal period of time or the whole base. The presence of virtual
attributes of search, such as the cycle, the satellite series, and the
number of he orbit, provides accomplishment of automatic selection without
involving the supplementary data.
The so-called map of search is compiled before the search
by using the selected criterion of search on the basis of inverting the
files procedure. The map is a succession of the disk number for the multi-volume
data base, and the names of the files, the information from which satisfies,
in the first approximation, the given logic of the search. This rocedure
greatly increases the rate of search and selection. Moreover, the system
automatically requests the disk necessary for reading. We should note that
in the process of search and selection, the system operates only with the
disk umber, the name of the file and the number of recording; consequently,
the volume of the service file with the results f selection is small.
The important peculiarity of the system is the availability
of multistage selection of information. After completion of he first stage
of selection into the subbase-1 and the analysis of the selected information,
we can undertake the search with previously selected data by using any
new or already existing criterion and store the data into the subbase-2.
After selection of information, the system allows copying of selected information
either in the symbolic format into the file, r in the binary format with
merging of the entire bulk of information within one data base. On this
step one can specify the parameters necessary for the next steps of processing.
One can also to conserve the binary format of distributive or to decode
the data if the data is output in the binary format.
The system allows to conduct simultaneous selection and copying
of information into the user's data base. This data ase retains the inverted
structure of the initial CD-ROM. The system allows to display values of
parameters of elected records and to draw plots of selected temporal data
series without termination of the search mode.
The block of express-analysis and preliminary data processing
allows to identify selected data with tracks of satellite, o determine
the type of these tracks (ascending or descending), and to check their
position in space. It allows also to display variations of any parameter
along the track, or on some part of it. The function of improvement of
the values of sea surface heights by introducing various corrections and
the function of visualization of these values as deviations rom the reference
surface (for example, from the geoid in the dynamic topography of the ocean)
are realized in this lock.
The space structure of the studied parameter is analyzed
by averaging the data on a selected grid at the knots or centers of its
cells with subsequent visualization of the obtained field in the form of
isolines; an opportunity is provided, by analogy with the previous statement,
to correct the values of heights of sea surface by introducing different
corrections, or by the display of deviations from the standard surface.
The research was undertaken with support from the Russian
Basic Research Foundation (Project ¹ 96-07-89315).
© Geophysical Center RAS, 1998
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