  Interferometers require accurate determination of the array configuration in
order to produce reliable observations. A method is presented for finding the
maximum-likelihood estimate of the telescope geometry, and of other
instrumental parameters, astrometrically from the visibility timelines obtained
from observations of celestial calibrator sources. The method copes
systematically with complicated and unconventional antenna and array
geometries, with electronic bandpasses that are different for each antenna
radiometer, and with low signal-to-noise ratios for the calibrators. The
technique automatically focusses on the geometry errors that are most
significant for astronomical observation. We apply this method to observations
made with the Very Small Array and constrain some 450 telescope parameters,
such as the antenna positions, effective observing frequencies and correlator
amplitudes and phase shifts; this requires only ~ 1 h of CPU time on a typical
workstation.
