A calibrated three-dimensional optical measuring apparatus for the three-dimensional measurement of geometric parameters of a rope has a frame defining and arranged around a rope receiving cavity. A plurality of image acquisition devices is configured to acquire a plurality of digital images of at least one region of an outer surface of the rope. The image acquisition devices are fixed to the frame and arranged around the rope when the calibrated three-dimensional optical measuring apparatus receives the rope in the rope receiving cavity. An attachment device is configured to constrain the calibrated three-dimensional optical measuring apparatus to the rope in a relatively translatable manner with respect to the rope. An electronic digital image processing device is configured to process a multiplicity of digital images and obtain a three-dimensional photogrammetric reconstruction of points of the digital images of the rope acquired by the image acquisition devices.