At each sampling point, ellipsoids represent the square root of the empirical covariance matrix of the initial speed vectors (left hand side) or displacement field (right hand side). With PLC method, extremal points are supposed to be matched: this induces a high variability at the extremities of lines (area 1, right). This is avoided by the current approach (area 1, left). With PLC, each line is registered individually: the variance can vary dramatically where lines cross (area 2, right). This situation can occur where a sulcus has a branch, in ”Y“-shape configuration, and the junction may not be considered by the PLC approach. The global regularity constraint of CDR leads to smoother results (area 2, left).