This paper describes a precise positioning method for autonomous driving system. Global navigation satellite system (GNSS) is widely used to estimate the vehicle position. The purpose of this paper is improving the accuracy of single-frequency real time kinematic (RTK)-GNSS positioning. In general, it is difficult to solve GNSS carrier phase ambiguity using a single-frequency GNSS receiver in multipath environments. Therefore, we propose a method consists of two approaches to solve this problem. First, reliable GNSS satellites are selected based on the difference of the signal to noise ratio (SNR) between the vehicle and the base station. Second, inertial navigation system (INS) is integrated in least-squares ambiguity decorrelation adjustment (LAMBDA) method to improve the ambiguity resolution performance. As a result of evaluation, the proposed method is effective on improvement of GNSS positioning accuracy.
