Generation of a reference standard from multiple manually annotated datasets is a non-trivial problem. This paper discusses the weighted averaging of 3D open curves, which we used to generate a reference standard for vessel tracking data. We show how weighted averaging can be implemented by applying the Mean Shift algorithm to paths, and discuss the details of our implementation. Our approach can handle cases where the observer centerlines take different branches in a natural way. The method has been evaluated on synthetic data, and has been used to generate reference centerlines for evaluation of vessel tracking algorithms.