1. A method of calibrating a photolithographic system, comprising: obtaining a plurality of measured dimensions of circuit patterns generated using a configuration of a photolithographic process; generating a plurality of estimated dimensions of the circuit patterns using a model of the configuration of the photolithographic process; for certain of the circuit patterns, calculating a polynomial fit between the estimated dimensions and predefined parameters related to the configuration; and calibrating the photolithographic process based on the polynomial fit, wherein calibrating the photolithographic process includes the step of minimizing differences between the estimated and measured dimensions using an optimization algorithm.