(a) Perturbed PFSS field generated from GONG magnetogram from 2014 January 10. This is the starting point of the model field. (b) Ideal model field from which optimization constraints were drawn. (c) Result of optimization based on ideal constraints with no error in the measured orientation angles. (d)–(f) The model field after optimization with constraints with normally distributed error with standard deviation of ﹩{\sigma }_{\theta }=2^\circ ﹩, ﹩10^\circ ﹩, and ﹩20^\circ ﹩.