A Resolution Method for Ionoshperic Delay withOptimal Combination of Three-Frequency Data

Objective Usually,it takes a long time to get the double-differential ionoshperic delay using dual-fre-quency observations.To solve this problem,based on the three-frequency carrier,a new ionoshpericdelay estimation method for long distance is proposed.First,the optimal combinations for ionoshpericdelay resolution are selected according to error characteristics of the different combinations.Then,in-itial ionoshperic delay is solved using optimal combinations ambiguity.At last,an idea which is simi-lar to carrier-smoothed code through hatch filter is introduced to improve the initial ionoshperic delay.Experimental show results that the estimation accuracy of double-differential ionoshperic delay can bein 2cm with only dozens of epochs or even less.It realizes the real-time and high accuracy resolutionfor long distance double-differential ionoshperic delay.