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: http://www.atnf.csiro.au/computing/software/gipsy/gds/structure.html
Дата изменения: Unknown Дата индексирования: Fri Jan 16 22:27:30 2009 Кодировка: Поисковые слова: solar system |
The image data is stored in a `crystalline' structure with a virtually unlimited (up to 20) number of dimensions. Image data is only referenced using coordinates on symbolic axes. File coordinates are hidden from the user.
Subsets should not be confused with frames. A frame is a part of a subset.
Most descriptor items have the same format and semantics as FITS header items. The descriptor system however is capable of storing a wide variety of data formats, including tables.
Every axis of a set has a name, a length in pixels and physical coordinate system associated with it (all specified in the descriptor). Elements of the data set can be identified using an N-dimensional grid coordinate.
A separate document describes how the user can specify subsets, coordinates, frames, etc.
If it is really necessary to use Unix commands on descriptor and/or image files, one should make sure that there is no active GDS server process. This can normally be deduced from the absence of any files .gds_sockets* in the user's home directory. When the user did not have a GIPSY session active for some time (> 5 minutes), one can also assume that no GDS server is active.