TRD tracklet to TPC track residuals in $y$ as a function of the $z$ coordinate of the TPC track ($z_{\rm track}$)for supermodules 2 (left) and 6 (right). The colour code is linear in the number of tracks. The upper and lower panels show the situation with the survey alignment and with in addition the external alignment, respectively. The data are from a 2012 run of \pp collisions with B = $-$\SI{0.5}{\tesla}. The alignment set used for the lower plots was deduced from the same run. The internal alignment is applied in all four cases.