  The BABAR Silicon Vertex Tracker (SVT) is a five-layer double-sided silicon
detector designed to provide precise measurements of the position and direction
of primary tracks, and to fully reconstruct low-momentum tracks produced in
e+e- collisions at the PEP-II asymmetric collider at Stanford Linear
Accelerator Center. This paper describes the design, implementation,
performance, and validation of the local alignment procedure used to determine
the relative positions and orientations of the 340 SVT wafers. This procedure
uses a tuned mix of in-situ experimental data and complementary lab-bench
measurements to control systematic distortions. Wafer positions and
orientations are determined by minimizing a chisquared computed using these
data for each wafer individually, iterating to account for between-wafer
correlations. A correction for aplanar distortions of the silicon wafers is
measured and applied. The net effect of residual mis-alignments on relevant
physical variables is evaluated in special control samples. The BABAR
data-sample collected between November 1999 and April 2008 is used in the study
of the SVT stability.
