Aiming at the problem of low searching efficiency and fixing success ratio exits in the methods for ambiguity resolution commonly used in geometry-based and geometry-free model

a modified three carrier ambiguity resolution method

MTCAR is proposed. The new method selects two combinations of extra wide lane which have excellent characteristics. The geometry-free model is used to fix their ambiguity

and on this basis

ambiguity of wide lane which has better error characteristics can be obtained. The ambiguity of narrow lane is fixed by using geometry-based model with the help of the wide lane. The ambiguity of each original carrier can be restored. Experimental analysis is carried out by Beidou triple-frequency measured data. Experimental result shows that the ambiguity fixing success rate of MTCAR is prior to LAMBDA of geometry-based model and TCAR of geometry-free model. Resolving efficiency is improved by about 60 % compared with the most commonly used LAMBDA algorithm.