1. A method for determining a registration error of a feature on a mask, the registration error indicating a deviation of a nominal position of the feature from its actual position on the mask the method comprising: providing a first aerial image that was captured by a position measuring device and includes at least said feature, said feature comprising a registration pattern or marker, simulating, from pattern specifications of the mask, a second aerial image that includes at least said feature, taking into account at least one effect that causes distortion of said first aerial image, and determining the registration error of said feature as the distance of the position of said feature in said first aerial image from the position of said feature in said second aerial image; wherein said second aerial image is simulated, on the basis of the pattern specifications of the mask, as a transmission function that has, at least in part, a higher resolution than said first aerial image.