HFWG Recommendation R6:
On the minimum and maximum actual and legal values within columns of FITS tables
(Approved: 1993 Aug 27)
If it is necessary to use keywords to store the minimum and maximum
values contained within column n of a FITS table, the following
keywords should be used:
respectively. These keywords are directly analogous to the
DATAMIN
and DATAMAX
keywords used in
association with the primary array and have been adopted elsewhere
within the FITS community.
If it is necessary to use keywords to store the minimum and maximum
legal values that may be stored within the elements of column
n of a FITS table, the following keywords should be used:
respectively. The following
recommentions are also made for clarity:
- The datatype of the keywords should be the same as that of the table
column (n) to which they refer.
- The keywords refer to all elements of a vector column.
- These keywords impose no constraints or information regarding the
meaning of any null data values within the data.
- The values of the keywords should be such that they
should be compared to the data values stored in the column
after those data values have been multiplied by/added
to the values stored in the corresponding
TSCAL
n and TZERO
n keywords.
- It should not be forbidden to have values of
TDMIN
n less than TLMIN
n or
TDMAX
n greater than TLMAX
n, leaving
it to individual applications as to what such situations imply.
- If the keyword for the minimum value be greater
than that for the maximum
value (i.e.
TDMIN
n is greater than TDMAX
n or
TLMIN
n is greater than TLMAX
n
as appropriate), then this
should be taken to mean that the values had not been defined.