Study Of The GNSS Single Epoch Ambiguity Resolution

The key technology in the high-precision GNSS navigation service is to determine the ambiguity of the carrier phase.Once the ambiguity is correctly fixed,the centimeter-level or millimeter-level positioning accuracy can be achieved.However,due to the effect of the observation environment,satellites will not be detected,in this circumstance,the ambiguity will be re-initialized.This process limits the continuity and real-time of positioning on a certain level.GNSS single epoch solving method can solve integer ambiguity by an epoch and ignore the effect of cycle slip by constructing prior constraints.Therefore,it is significant to study GNSS single epoch algorithm.This article focuses on the following aspects of single ambiguity fixed:(1)A single epoch ambiguity fixed algorithm suitable for deformation monitoring.According to the correlation between the stations,the initial observations are used to solve the initial double-difference ambiguity,and the receiver clock and some other unknowns are treated as parameters,so that the deformation information can be directly extracted.By averaging the long-term deformation information,the short baseline error is about 1 mm in the N and E directions and about 4 mm in the U direction and as the baseline increases,the error of the calculation gradually increases,so this method is only suitable for short baseline deformation monitoring.(2)Ambiguities fixed by single epoch in short baseline single epoch.In the short baseline single epoch fixed ambiguity,the ambiguity of the IGSO and MEO satellites is fixed at the base of wide lane ambiguity,and then the IGSO and MEO satellite ambiguity values are used as constraints to fix the GEO satellite ambiguity.The morbidity of the wide-lane ambiguity time equation is solved by a regularization method based on singular value decomposition.Two groups of baselines with lengths of 4.4m and 2.32km were used to verify the algorithm.The results showed that the success rate of the single epoch wide-lane ambiguity of the BDS/GPS combined system was 100%;the success rate of the original ambiguity was over 90%,which was better than the conventional method.Fixed Beidou satellite ambiguity success rate has improved.In addition,the positioning accuracy in the N,E,and U directions reaches centimeters to millimeters.(3)Ambiguities fixed by single epoch in medium-long baseline.Aiming at the fixed ambiguities of medium and long baselines,we propose to use the regularization method twice to improve the ill-conditioned problem of single epoch observation equations.The regularization matrix is constructed by singular value decomposition of the coefficient matrix of the carrier double difference equation.Using the two sets of GPS/BDS data with lengths of 56.225 km and 170.176 km,respectively,the results show that:after one regularization method,the rate of ambiguilty fixed in two baseline all reach 100%,however,the success rate of the original carrier ambiguity is very low.Therefore,after the wide-lane ambiguity was successfully fixed,the non-ionosphere combination was combined and use the regularization method again,For the 56.225km baseline,the positioning accuracy in the N and E directions reached mm-level after two regularizations,and reached the cm-level in the U-direction.For the 170.176km baseline,the positioning accuracy in the N,E,and U directions after the two regularizations reaches the level of cm.