Comparison of the slant wet delay of GNSS signal between parameterized model and numeric weather model calculations

We examined the accuracy of wet slant delay extracted by double differenced method against ORSM –an operating numeric weather model in the Hong Kong observatory on the near real time basis.The accuracy of the DD method is primarily dominated by that of the estimate of wet zenith delay and multiplied by the wet mapping function.It determines the wet slant delay with 3 mm bias and 27 mm root mean square error against the ORSM model.At low elevation angle,the mean absolute difference can reach 30mm.