The invention relates to a calibration method for a printer having a mechanism for advancing a medium in a direction of media advance comprising the following steps: a—providing a printhead, the printhead having a swath height in the direction of media advance; b—providing an estimate of either the swath height or the characteristic of the mechanism; c—printing a base pattern on a medium using the printhead; d—printing an overlay pattern on the medium using the printhead to form an interference pattern; e—advance the medium of a predetermined distance using the mechanism at a time between the printing of the base pattern and the printing of the overlay pattern; f—analyze an optical evaluation of the interference pattern; g—evaluate as either: i—the swath height if the characteristic of the mechanism is known or estimated; or ii—the characteristic of the mechanism if the swath height is known or estimated.