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: http://www.adass.org/adass/proceedings/adass03/P3-25/
Дата изменения: Thu Aug 26 23:22:21 2004 Дата индексирования: Tue Oct 2 05:32:17 2012 Кодировка: Поисковые слова: guide 8.0 |
VOTable java Streaming Writer is an API library for writing data in VOTable format. Streaming support is provided to deal with very large VOTable files without running out of memory. The writer does not create a tree structure in memory, so that the memory requirement is substantially reduced and very large VOTables can be written.
This is a tool for converting ASCII or FITS files to VOTable format. For ASCII files, it supports both ASCII files with column delimiters and ASCII files with fixed width columns. For FITS files, it supports FITS ASCII and binary tables. A number of useful data processing, browsing and visualization tools are available to deal with data in the VOTable format. But, most of the astronomy legacy data exists in the form of ASCII catalogues and FITS tables. To be able to use the new VOTable packages on legacy data, it is necessary to have a converter which transforms that data to the VOTable format. Tools are also needed to transform the outputs generated by various application packages to the VOTable format. We describe such a tool here.
The tool first determines which of the two types the ASCII file is. It then determines the delimiter, or the width of individual column depending upon the file type. It reports to the user the number of columns detected, and this number can be changed if required in special cases. Finally, it determines the data type of individual columns by scanning the first few lines in the file and displays the file metadata which can be edited. When the file is converted to VOTable format, it is written to output stream using the VOTable Java Streaming Writer. The tool works in streaming mode by reading the ASCII file one line at a time and writing the VOTable one row at a time. It can therefore be used to convert big ASCII files to VOTable files without running out of memory.
The tool makes use of nom.tam.fits library to read FITS files. Metadata is read from the headers of individual Header Data Units. Metadata is displayed to the user for confirmation and it can be edited as well. After the FITS tables are converted to VOTable, the tool makes use of the VOTable Java Streaming Writer to write the data to the output stream.
VOPlot is a tool for visualizing astronomical data. It is an application for plotting different astronomical graphs using data stored in VOTable format. VOPlot makes use of VOTable Java Streaming Writer to export the data in VOTable format. See Kale et al (2004) for a description of VOPlot.
Kale, S. 2004, this volume, 350