Standard NetCDF Attribute Usage

These attributes are defined by the NetCDF standard itself [1].

• units - String which specifies the units of a variable's data, if applicable. The units should be compatible with the UCAR udunits library. In MINC 1.0, this attribute is generally included for informational purposes only and is not interpreted by the MINC library code.
• long_name - String giving a human-readable textual description of the variable. Included for informational purposes.
• valid_range - A vector of two numbers which specifies both the minimum and maximum valid values for this variable. Values outside this range must be treated as missing or uninitialized. In MINC, the order of the two values in the vector is not significant.

  This attribute must not be defined if either the valid_min or the valid_max attributes are defined.

  These attributes should be considered mandatory for the MINC image variable, unless the variable uses the default range, which is defined to be the full range of an (possibly signed or unsigned) integer type or the interval [0.0, 1.0] for floating point types. They are not required for any other MINC variable.

• valid_max - Scalar number which gives the maximum value allowed for the variable. Note that the presence of valid_max and valid_range are mutually exclusive.

• valid_min - Scalar number which gives the minimum value allowed for the variable. Note that the presence of valid_max and valid_range are mutually exclusive.

• _FillValue This is a scalar numeric value which gives the value to be used to fill in any value which is not explicitly written, or which falls outside the defined valid range of the data.

• history - A global string attribute for an audit trail. This is a character array with a line for each invocation of a program that has modified the dataset. All MINC and NetCDF applications should append a line containing: date, time of day, user name, program name and command arguments for each processing step. This attribute should be considered mandatory.

• title - A global string attribute which provides a description of the MINC file's contents. In practice this is optional and somewhat rarely used.