The invention relates to a position determining device for determining a position of an elongate object within a tubular structure, said position determining device comprising a first providing unit for providing a first distribution of curvature values at a plurality of first points along a path within the tubular structure. The position determining device further comprises a second providing unit for providing a second distribution of strain values or of curvature values at a plurality of points along the object, and a position determining unit for determining the position of the object relative to the path on the basis of the first and second distributions.