北斗（BDS）与GPS联合定位技术是当下研究的热点，有益于推动BDS走向全球，为我国BDS和其它导航系统深度融合奠定基础。由于定位解算模块是接收机定位关键部分，本文主要对BDS/GPS定位解算算法进行研究与仿真分析。主要工作和创新点如下： 本文以BDS/GPS双模接收机定位研究方法及导航技术为基础，分析了单点定位技术、载波相位平滑算法、系统兼容性及定位中的误差源，建立了BDS/GPS双模接收机定位模型，并依据用户的运动状态，给出了静止用户与低动态用户的系统状态模型。 针对BDS/GPS双模卫星多、冗余量增大的情况，在分析已有选星算法的前提下，提出基于卫星角度的改进选星算法，该算法利用卫星间视线向量构造的代价函数最大值剔除了低仰角中起相同作用的卫星。仿真对比发现，在DOP值精度为优的条件下，改进选星算法比其它选星算法的运算量小，定位结果误差小、精度较高。 BDS/GPS双模定位解算中，针对单频载波相位平滑伪距法因初值不准和电离层误差累积而导致滤波器发散的问题，引入基于卡尔曼滤波的载波相位平滑伪距法，该方法能规避滤波器发散的风险，提高定位结果的可靠性。其次，在研究了最小二乘法和卡尔曼滤波法的基础上，将最小二乘法和卡尔曼滤波两种算法联合，通过对卡尔曼滤波初始化、对协方差矩阵的正定性与对称性处理，保证了联合解算算法的有效性。仿真结果表明，该算法定位误差小，稳定性高。 本文从卫星可见性、精度因子值、定位精度和定位速度四方面对所研究的算法进行仿真验证。仿真结果表明，BDS/GPS双模定位结果误差小，实时性好，稳定性高。其中，DOP值最大2.6135，三个坐标轴上平均误差均小于2.2米。

The joint positioning technology of Beidou (BDS) and GPS is a hot topic of current research, which is beneficial to promote the BDS to the whole world and lay a foundation for the deep integration of BDS in China and other navigation systems. Since the positioning and solving module is a key part of receiver positioning, this thesis mainly studies and simulates the BDS/GPS positioning algorithm. The main work and innovations are as follows: Based on the BDS/GPS dual-mode receiver positioning research method and navigation technology, the single point positioning technology, smoothing algorithm, system compatibility and error sources in positioning are analyzed in this thesis. The BDS/GPS dual-mode receiver positioning model is established. According to the user's motion state, the system state model of static users and low dynamic users is given. Aiming at a number of BDS/GPS dual-mode satellites and the increase of redundancy. Under the premise of analyzing existing star selection algorithms, an improved satellite selection algorithm based on satellite angle is proposed. The algorithm uses the maximum value of the cost function constructed by the inter-satellites line of sight vector to exclude satellites that play the same role in low elevation angles. The simulation comparison shows that under the condition that the precision of DOP value is excellent, the improved satellite selection algorithm has less amount of computation than other satellite selection algorithms. The result of positioning has low error and high precision. In the BDS/GPS dual-mode positioning solution, the single-frequency carrier phase smoothing pseudo-range method causes the filter divergence problem due to the initial value misalignment and the ionospheric error accumulation, and the carrier phase smoothing pseudorange method based on Kalman filter is introduced. The method can avoid the risk of filter divergence and improve the reliability of the positioning result. Secondly, on the basis of studying the least squares method and Kalman filter method, the least squares method and Kalman filter algorithm are combined. By initializing the Kalman filter and treating the positive definiteness and symmetry of the covariance matrix, the effectiveness of the joint solution algorithm is guaranteed. The simulation results show that the algorithm has low positioning error and high stability. In this thesis, the algorithms researched are verified by four aspects: satellite visibility, accuracy factor value, positioning accuracy and positioning speed. The simulation results show that the BDS/GPS dual-mode positioning results have small error, real-time performance good and high stability. The DOP value is at most 2.6135 and the average error on all three axes are less than 2.2 meters.