1. A lithographic apparatus comprising: an illumination system configured to condition a radiation beam; a support structure configured to support a patterning device, the patterning device being configured to pattern the radiation beam; a projection system configured to project a patterned radiation beam onto a substrate; and an inspection apparatus comprising: a detector configured measure a property of radiation reflected by the substrate having a device feature in a chip area and a target; and a processing unit operatively coupled to the detector and configured to determine an overlay error of the device feature by: determining an overlay error of the target, determining a difference between the determined overlay error of the target and the overlay error of the device feature due to a characteristic of the lithographic apparatus, determining a difference between the determined overlay error of the target and the overlay error of the device feature due to a difference in position between the target and the device feature on the substrate, and determining a difference between the determined overlay error of the target and the overlay error of the device feature due to a characteristic of the device feature.