Itįollows that multiple levels of compression should be available: Other use cases may be less tolerant to the loss of fidelity in the data, e.g. Some usage casesĬan expect large ratios in compression examples include visual data exploration, draft mosaicing,Įtc. Should occur only at the point where an image is to be displayed or used. Latency in service time and limited ability to serve a variety of users. Unreasonable computational and memory demands upon the server, leading to a large If the imagery mustįirst be decompressed, and then re-compressed to address a users needs, this will place Resolutions and qualities directly from the compressed representation. However, it should be possible to access image regions, Compression significantly reduces the cost of storage, Storage device that is provided through VOSpace, which is another IVOA standard.įurther, we will demonstrate that radio astronomy imaging data can be effectively compressed,Īnd the error due to the compression can be controlled. The resulting files can then be stored on a local computer or a virtual network Retrieve image files in one or more formats, depending on the archive capabilities (e.g. Of the International Virtual Observatory Alliance (IVOA) 4 4 4 that provides aĭata from a variety of astronomical image repositories.īy using SIAP the user can query compliant archives in a standardised manner and The example of such a framework is Simple Image Access Protocol (SIAP) 3 3 3 /Documents/SIA/ If coterminous regions are required, several cutout files would be Of an image-cube (cutout) is produced in one of the image formats, and presented to the Image files or CASA tar-balls are normally retrieved from an archive and stored on a localĬomputer for exploration, analysis or processing purposes. These formats provideīoth, portability and access to image data. CASA data is usually distributedĪs an archived file created by using common archiving software, such as CASA, on the other hand, uses a different approach representing anyĭata as a hierarchical structure of directories and files. LOFAR HDF5-based format (Anderson et al., 2011).įITS and HDF5 are, in general, single self-describing files containing the image data, as Currently, most radio astronomy imaging data is stored and distributed in one of threeįormats: FITS (Flexible Image Transport System) ( Pence et al., 2010) ĬASA Image Tables 1 1 1 and newly developed by
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