Data Formats

Table Format

In addition to the image data formats described above, STSDAS supports a table format. The table format is especially useful for storing the output of certain data processing tasks (like a list of star positions and magnitudes from daophot) and for exchanging data between different applications packages. Tasks that create, edit, and perform other functions with tables are found in the STSDAS ttools package (see "STSDAS Tables: the ttools Package" on page 68).

STSDAS tables are stored in a binary format, and table data is a mix of character string, integer, short integer, boolean, and single and double-precision floating point. Each column must be of the same predefined format, and each row must contain the same number of columns. Figure 3.7 shows how a STSDAS table is structured.

Each table column has four attributes:

Name: String of up to 19 characters, case insensitive. Similar names differing only in the use of upper or lower case are indistinguishable.
Data type: Real, double, integer, boolean, or text.
Display format: The specification for printing the contents of the column, used only for printed listings. Note that this is related to but distinct from the internal data type. That is, a double-precision column may be printed with limited precision although any computations using that column would be carried out in full precision.
Units: A string of up to 19 characters. May be used by some tasks, for example, to distinguish between right ascension in hours or degrees. The default is null.

STSDAS Table Structure

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