From the comparison between the PLV results derived from the astrometric and gavimetric techniques at interannual time scales, one can conclude that the interannaul PLV along the meridian is in the order of 0.02'' in the case of Jozefoslaw observatory, and it is possible to measure it in practice by the astrometric technique.
Acknowledgements
The author is indebted to Prof. Marcin Barlik of the Warsaw University of Technology for his kind provision of the plumb line variation results at Jozefoslaw Observatory and the related informations. Without his help, the work could not have been done. The author is also grateful to Dr. F. Barlier for his helpful comments. The study has been supported by the Chinese National Natural Sciences Foundation No. 19373018 and 19673011, and also the NSF International Program Grant through the University of Texas, Department of Geological Sciences, Professor Clark R. Wilson (Principal Investigator).