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Дата изменения: Thu Apr 20 19:34:32 2000 Дата индексирования: Tue Oct 2 06:22:39 2012 Кодировка: Поисковые слова: south pole |
The Wideband Arecibo Pulsar Processor - File Format Page |
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WAPP File FormatWAPP files have three sections that appear sequentially in this order: an ASCII header description, the binary header, and finally the actual binary data. The first section is a raw copy of the C-language include file (wapp_header.h), terminated with a single null character. This is included for reference only and does not include any information specific to the observation. After the ASCII header comes the actual header values that describe the observation. . The WAPP realtime observation engine does not produce files larger that 2 Gbytes. At one time this represented a fundamental limit to Linux files. However, the reason behind this limit is to avoid difficult to manage megafiles. As a consequence, most observations produce a sequence of data files. Each file will have it's own header, even when the files are simply continuations of a single observation. The only difference in header values in this case will be the timeoff parameter, which indicates the time offset from the start of the observation. The most recent version of this structure is maintained in the ~wapp/include/wapp_header.h subdirectory. Although the include file is available, it is recommended that the user extract the ASCII header from the WAPP data files. This approach will avoid problems with header versions. To view the header file embedded in each data file, type the following: more wapp.nnn[ret]
WAPP files are written by a i386 Linux machine and use the native byte ordering of that machine: little endian. Thus in memory a 16 bit integer will have it's most-signficant byte appear first. For example, decimal integer 4600 (1234 hex) would appear in memory as follows: ![]() The final portion of the WAPP data file is the actual correlation values. It is written as raw unsigned integers value of 16 or 32 bits (see lagformat). It is written such that lag 0 appears first, then lag 1, etc. If there are multiple IFs, they appear as A, then B, then ?x?(AxB or BxA) and finally ?x?. WAPP Header Parameter DescriptionThe following table describes the various parameters in the WAPP Header file. The details of this header may evolve, so it is always useful
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