Multipath (MP) reception has been among the main issues for accurate and reliable positioning in urban environments. It has been shown to introduce positioning errors of up to tens of meters for conventional two-step (2SP) receivers. The direct position estimation (DPE) has been introduced as a more robust positioning algorithm compared to the conventional two-step (2SP) receivers in terms of MP mitigation. However, its high computational load prevents DPE from real-time positioning for commercial receivers. Thus, we present a novel grid-based maximum likelihood estimation (MLE) algorithm based on DPE by making use of pseudorange measurements to obtain the correlogram on a predefined searching space. Unlike DPE, which performs correlations at the intermediate frequency (IF) level, correlations are done by directly comparing the code phase of each candidate position, velocity, and timing with the incoming pseudorange. This way, the proposed method retains MP mitigation properties from DPE through the use of MLE from DPE and allows for a significantly reduced computational load compared to DPE. The proposed method was tested with both open-sourced datasets collected in urban environments as well as IF simulation data, and its performance is evaluated against a 2SP receiver. Results show that the proposed method manages to acquire the MP mitigation capability of DPE and outperforms 2SP by up to around 23% in the tested urban datasets and 91% in the simulation data, at a much-reduced computational time. The resilience of our proposed method against MP and NLOS could even potentially offer applications in geodetic networks, where robust estimators are traditionally employed to counteract outliers. 

多路径（MP）接收一直是城市环境中准确可靠定位的主要问题之一。事实证明，它会给传统的两步 (2SP) 接收器带来高达数十米的定位误差。与传统的两步 (2SP) 接收器相比，直接位置估计 (DPE) 是一种在 MP 缓解方面更稳健的定位算法。然而，其高计算负载阻碍了DPE对商业接收器的实时定位。因此，我们提出了一种基于 DPE 的新颖的基于网格的最大似然估计（MLE）算法，通过利用伪距测量来获得预定义搜索空间上的相关图。与在中频 (IF) 级别执行相关的 DPE 不同，相关是通过直接将每个候选位置、速度和定时的码相位与输入伪距进行比较来完成的。这样，所提出的方法通过使用 DPE 的 MLE 保留了 DPE 的 MP 缓解特性，并且与 DPE 相比可以显着减少计算负载。该方法使用在城市环境中收集的开源数据集以及 IF 模拟数据进行了测试，并针对 2SP 接收器评估了其性能。结果表明，所提出的方法能够获得 DPE 的 MP 缓解能力，并且在测试的城市数据集中优于 2SP 约 23%，在模拟数据中优于 2SP 约 23%，同时大大减少了计算时间。我们提出的针对 MP 和 NLOS 的方法的弹性甚至可以在大地测量网络中提供应用，在大地测量网络中，传统上采用稳健的估计器来抵消异常值。