Calibration of models for manufacturing processes that are subject to circuit layout proximity effects is performed, including optical proximity correction (OPC) model calibration. A target structure is produced using a layout and a manufacturing process. The target structure is illuminated and an electromagnetic scattering property is detected. A manufacturing process model for simulation of the manufacturing process is produced, which comprises at least one manufacturing process parameter determining a model electromagnetic scattering property using the manufacturing process model and the layout. The model electromagnetic scattering property is compared to the detected electromagnetic scattering property and based on the result of the comparison, calibrated manufacturing process parameters are output for calibrating the manufacturing process model. The determining and the layout may include determining structural information corresponding to the target structure using the manufacturing process model and determining the model electromagnetic scattering property using the structural information.