For documentation on how to use this sub-system, see
atmlab/documentation/collocations.pdf.

The files in satreaders/ have the task to read a particular granule from a
particular dataset and arrange it in a structure that contains at least lat,
lon and time, where the number of rows in each three should be the same, and
the number of columns in lat and lon should be equal, and the number of
columns in time should be 1. This convention was initially designed for the
portable use of collocation codes.