  The central component of the CMS detector is the largest silicon tracker ever
built. The precise alignment of this complex device is a formidable challenge,
and only achievable with a significant extension of the technologies routinely
used for tracking detectors in the past. This article describes the full-scale
alignment procedure as it is used during LHC operations. Among the specific
features of the method are the simultaneous determination of up to 200,000
alignment parameters with tracks, the measurement of individual sensor
curvature parameters, the control of systematic misalignment effects, and the
implementation of the whole procedure in a multi-processor environment for high
execution speed. Overall, the achieved statistical accuracy on the module
alignment is found to be significantly better than 10 micrometers.
