Influence of the Cut-off Elevation Angle and Elevation-Dependent Weighting on Parameter Estimates: A Case of CONT05

In this paper, results are presented on studies which have been performed to investigate the impact of the cut-off elevation angle (CEA) and elevation-dependent weighting (EDW) on the EOP estimates and baseline length repeatability. For this test, CONT05 observations were processed with different CEA and EDW, keeping all other options the same as used during the routine processing. Uncertainties and biases, as well as correlations between estimated parameters have been investigated. It has been shown that small CEA, up to about 8--10 degrees does not have large impact on the results, and applying EDW allows us to get better result (smaller errors). However, this result has been proven with standard geodetic VLBI observations, where rather few observations were made at low elevations. Perhaps, special R&D sessions with more uniform distribution of observations over elevation may be useful for more detailed study on the subject.