Software package sotid is for computing site displacements due to the solid Earth tides using the frequency domain approach. The algorithm is described in the paper L. Petrov, C. Ma Study of harmonic site position variations determined by VLBI, Journal of Geophysical Research, vol. 108, No. B4, 2190, doi: 10.1029/2002JB001801, 2003.
The precision of the computation is better than 0.1 mm. The accuracy of the computation depends on the model and is deemed to be better than 1 mm.