Measurements of interannual variation of the vertical at Jozefoslaw by astrometric and gravimetric observations

Jozefoslaw astronomical and geodetical observatory at Warsaw is the place where parallel observations of astrometric latitude (since 1959) and meridional plumb line variations from gravimetric methods (since 1976) have been carried out continuously over the past 20 years. The observational data at this observatory have been analysed to confirm the reality of the plumb line variation results derived from the astrometric latitude residuals. Cross correlation analyses between the results of the two techniques have demonstrated that the interannual plumb line variations along the meridian detected by the astrometric technique is in good accordance with those from the gravimetric technique. The results shown in the paper can be considered as evidence of the existence of non-tidal plumb line variations at interannual time scales, of which the scale is about 0.02 " in the case of Jozefoslaw observatory, and the possibility in measuring them by astrometric techniques