1. A computer-implemented method comprising: simulating, using a processor, a second aerial image from pattern specifications of a mask, including determining said second aerial image as a matrix composed of pixels having intensity values, taking as a basis the pattern specifications of the mask in the form of a transmission function that has, at least in part, a higher resolution than a first aerial image of the mask that was captured by a position measuring device, the first aerial image having a feature, the second aerial images also having the feature; and determining, using the processor, a registration error of the feature on the mask based on a comparison of the simulated second aerial image and the first aerial image, the registration error indicating a deviation of a nominal position of the feature from its actual position on the mask.