  Magnetic flux synoptic charts are critical for reliable modeling of the
corona and heliosphere. Until now, however, these charts were provided without
any estimate of uncertainties. The uncertainties are due to instrumental noise
in the measurements and to the spatial variance of the magnetic flux
distribution that contributes to each bin in the synoptic chart. We describe
here a simple method to compute synoptic magnetic flux maps and their
corresponding magnetic flux spatial variance charts that can be used to
estimate the uncertainty in the results of coronal models. We have tested this
approach by computing a potential-field-source-surface model of the coronal
field for a Monte Carlo simulation of Carrington synoptic magnetic flux maps
generated from the variance map. We show that these uncertainties affect both
the locations of source-surface neutral lines and the distributions of coronal
holes in the models.
