This section contains background information and basic definitions.
It’s purpose is two-fold:
- Users and developers can learn or look up the nitty-gritty details how coordinates, times, … are defined and basic information about file and storage formats (e.g. how axis-information for multi-dimensional arrays can be stored in FITS files).
- Data format specifications can refer to the definitions in this section, e.g. we don’t have to repeat that the azimuth angle is measured east of north in each format specification where azimuth is used.