An apparatus is provided having a proximal end, a distal end, and an outer surface. The apparatus comprises a handle portion located near the proximal end of the apparatus, a supporting arm attached to the proximal end of the apparatus, the supporting arm having a tracking marker, a flexible tip portion located at the distal end of the apparatus, and a plurality of sensors located on the outer surface of the apparatus. The plurality of sensors each provides a signal representing information that is useable for determining deformation of the flexible tip portion. The apparatus may be either a sheath for covering a medical tool or the apparatus may be a medical tool.