Integer ambiguity resolution considerable improves the performance of precise point positioning (PPP). With the popularity of multi-frequency observations, multi-frequency PPP ambiguity resolution (PPP-AR) for GPS, BDS and Galileo has been well studied, whereas there is a lack of research on GLONASS triple-frequency PPP-AR. Fortunately, GLONASS currently transmits CDMA signals on the third frequency of two GLONASS-K and four GLONASS-M + satellites, making it possible to investigate the triple-frequency PPP-AR. To fully exploit GLONASS triple-frequency observation, this study proposes a CDMA + FMDA combined multi-frequency PPP-AR model with the careful consideration of GLONASS phase inter-frequency clock bias (IFCB) errors. The characteristics of GLONASS IFCBs and EWL UPDs are also well investigated. To verify our proposed model, tracking data of 14 stations is used to estimate uncalibrated phase delay (UPD) and another 6 stations are selected as users to perform PPP-AR. A time- and satellite-dependent IFCB of about 0.2 ~ 0.5 m is identified for GLONASS-M + triple-frequency observations. After the removal of the IFCB, the EWL, WL and NL UPDs of GLONASS satellites show remarkable stabilities at several hours. About 99.9% EWL, 98.7% WL and 99.4% NL residuals are within 0.15 cycles, which shows comparable accuracy compared with GPS. Based on the precise UPD products, GLONASS triple-frequency PPP-AR can be achieved. Compared with PPP float estimates, GLONASS triple-frequency PPP-AR improves the convergence time and 1-hourly positioning errors in the E, N and U directions from 14.5 min and [4.6 20.7 39.9] mm to 11.5 min and [3.1 4.6 14.1] mm, with an improvement of about 20.7% and [32.6% 77.8% 64.7%], respectively. However, limited by the number of datasets under current conditions, GLONASS triple-frequency PPP-AR exhibits insignificant improvement compared with the dual-frequency solution. After integrating GPS triple-frequency observations, results indicate that GLONASS + GPS triple-frequency PPP-AR exhibits significantly better positioning performance than the dual-frequency solution.

整数模糊度分辨率显着提高了精确单点定位（PPP）的性能。随着多频观测的普及，GPS、BDS、Galileo的多频PPP模糊度解析（PPP-AR）得到了很好的研究，而GLONASS三频PPP-AR的研究还比较缺乏。幸运的是，GLONASS目前在两颗GLONASS-K和四颗GLONASS-M+卫星的第三频率上传输CDMA信号，使得研究三频PPP-AR成为可能。为了充分利用GLONASS三频观测，本研究提出了一种CDMA + FMDA组合的多频PPP-AR模型，并仔细考虑了GLONASS相位间频时钟偏差（IFCB）误差。 GLONASS IFCB 和 EWL UPD 的特性也得到了深入研究。为了验证我们提出的模型，使用 14 个站点的跟踪数据来估计未校准相位延迟（UPD），并选择另外 6 个站点作为用户来执行 PPP-AR。对于 GLONASS-M + 三频观测，确定了约 0.2 ~ 0.5 m 的与时间和卫星相关的 IFCB。去除IFCB后，GLONASS卫星的EWL、WL和NL UPD在几个小时内表现出显着的稳定性。大约 99.9% EWL、98.7% WL 和 99.4% NL 残差在 0.15 个周期内，这与 GPS 相比具有相当的精度。基于精准的UPD产品，可以实现GLONASS三频PPP-AR。与PPP浮动估算相比，GLONASS三频PPP-AR将E、N和U方向的收敛时间和1小时定位误差从14.5分钟和[4.6 20.7 39.9]毫米改善到11.5分钟和[3.1 4.6 14.1]毫米mm，分别提高了约 20.7% 和 [32.6% 77.8% 64.7%]。但受限于当前条件下的数据集数量，GLONASS三频PPP-AR与双频方案相比提升并不明显。整合GPS三频观测结果表明，GLONASS+GPS三频PPP-AR的定位性能明显优于双频方案。