Determination and analysis of local seasonal terms of latitude variations

Local seasonal terms of latitude variations were determined on the basis of data of 17 BIH/IPMS stations andx, y, z data of the BIH global solution during the years 1967–1978. Some models for local correctionsR to the latitude introduced by the BIH are created. The correctionsR obtained from the least squares adjustment from one year data appear to be the best. The present study shows that it is necessary to determine these more frequently than once a year or to compute them for all stations simultaneously with the ERP. This will be particularly important in view of the future re-reduction of past astrometric data.