Abstract:This paper introduces the principle and effect of a new mapping function that could be used globally and easy to realize with software:the Global Mapping Function (GMF).Using the tropospheric delay obtained by the method of piecewise linear estimation as true value,we make comparisons between result from GMF and the true value,as well as NMF.By analyzing the differences among these three methods and their connections,some beneficial conclusions have been drawn.Numerical experiments show that GMF is an empirical mapping function with higher accuracy and easier implementation,thas is to very practical for us to choose.