1. A method of determining overlay error of a device feature, the method comprising: forming the device feature and a target on a substrate using a lithographic apparatus; measuring the overlay error of the target using an inspection apparatus; and determining the overlay error of the device feature based on the overlay error of the target measured using the inspection apparatus and a model that simulates a relative difference between the overlay error of the device feature and the overlay error of the target measured using the inspection apparatus; wherein the device feature is in a chip area of the substrate; and wherein the target is outside the chip area.