A COMPARISON OF DIFFERENT TROPOSPHERIC MAPPING FUNCTIONS BY ELEVATIONCUTOFF TESTS

The uncertainties in the ground surface meteorological parameters shou ld be introduced into atmospheric mapping function models, such as CfA 2.2 and UNSW931, etc. Although these models have been developed by the ray-tracing method according to a given tropospheric profile, these k inds of atmospheric modelling errors will have an effect on the estima tes of coordinates for very long-baseline interferometry (VLBI) sites. In this paper, several new mapping function models are examined. An a nalysis of VLBI data using different mapping function models indicated that the UNSW931 model has more powerful potential for the needs of e xtending VLBI measurements at low elevation angles below 5 degrees.