Accurate Measurements with Image-Assisted Total Stations and Their Prerequisites

Video theodolites were used in the 1980s for highly accurate, automated measurements. However, they disappeared from the market
and research on these instruments was done by only a few institutions using self-made prototypes. Because of the release of new-generation
image-assisted total stations (IATS) by different manufacturers since 2004, these instruments have become relevant again for broader user
groups. In this article, different error sources that occur when working with an IATS are assessed. The theoretical origins of these errors are
discussed, their dependence on the measurement geometry is worked out, and strategies for avoidance and modeling are provided. In experimental
geodetic network measurements, the impact of the different error sources on the results are evaluated. With standard deviations of a
few 0.01 mm for the estimated three-dimensional (3D) coordinates, it is demonstrated that the telescope camera of a modern IATS can be
used as a highly accurate measurement sensor.