A detection method for detecting a property of an extended pattern formed by at least one line generally extending in a first direction. The extended pattern is formed on a substrate or on a substrate table and may extend, for example, over a length of at least 50× the width of the line. The extended pattern is focus sensitive. The detection method includes moving the substrate table in a first direction and measuring along that first direction a property of the extended pattern. The property can be a result of a physical property of the extended pattern in a second direction perpendicular to the first direction. In a next step a calibration of the substrate table position can be derived from the measured position of the extended pattern.