BZERO
keyword (or the TZEROn
keyword in the case of binary
table columns with TFORMn = 'I') must also be included in the header
with its value set to 32768 so that FITS reading software will add this
offset to the raw values in the FITS file, thus restoring them to the
original unsigned integer values. Unsigned thirty-two-bit integers can be
represented in FITS files in a similar way by applying an offset of
2147483648 (231) to the data values.