The method involves performing continuous detection of camera images of auxiliary point marker (32) with camera. The continuous reading of passages in which pixels are read out with respect to current exposure value is performed. The continuous setting of current of interest-region (35a) on area sensor is performed based on set of previously recorded camera image. The interest area has defined subset of contiguous neighboring pixels of sensor. The current image position is determined based on current exposure values obtained from actual set located within areas of interest pixels. Independent claims are included for the following: (1) measuring device for continuously determining spatial position of several auxiliary-point markers; (2) measuring system for continuously determining spatial position of several auxiliary-point markers; and (3) computer program product for continuously determining spatial position of several auxiliary-point markers.