Abstract: The invention relates to a processing system (200) that is arranged to cooperate with an optical-shape-sensing-enabled elongated interventional device (1020, 1120, 1220, 1320, 1420), such as a catheter comprising an optical fiber. A reconstructed shape data providing unit (130) provides reconstructed shape data for the interventional device (1020, 1120, 1220, 1320, 1420). A virtual marking provider unit (140) provides at least one virtual marking (1020A, 1020B, 1101, 1102, 1103, 1201, 1203, 1204, 1301, 1302, 1401) based on the reconstructed shape data, for example as overlay to a x-ray image. The present invention thus turns any OSS-enabled device into a calibrated device, suitable for all kinds of live 3D measurements.