A method for calibrating a measuring system, which system comprises a structured light source, optics and a sensor. The light source is adapted to produce a light plane or sheet and the optics is located between the light plane and the sensor. The method is performed in order to obtain a mapping from the sensor to the light plane. In the method the light source is switched on such that the light plane is produced. In order to account for distortions due to the optics, a mapping calibration profile is introduced in the light plane, wherein the mapping calibration profile comprises at least three points forming a straight line. A non-linear mapping from the sensor to the light plane is then computed by using the at least three points. Next, in order to account for perspective distortions, a homography calibration profile is introduced in the light plane, wherein the homography calibration profile comprises at least four points the relative distance between which are predetermined. A homography from the sensor to at the light plane based on these four points is then computed. A calibration object for using in such a method is also presented.