qObservations are often available only at a few stations that are unevenly spaced in the domain
of interests.
qIn order to compute derivatives of the field variables, as would be required in diagnostic
studies or in the initialization of a numerical model, or simply to perform a sensible averaging process, one
often requires values of the variables at points on a regular grid.
qAssigning the best values at the grid points, given data at arbitrarily located stations and
perhaps a first guess at regular grid points, is what has traditionally been called objective analysis.
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