A unified PDOP evaluation method for multi-GNSS with optimization grid model and temporal–spatial resolution

Evaluation for Global Navigation Satellite System (GNSS) Position Dilution Of Precision (PDOP) is generally based on a simulated global grid with a specific Temporal–Spatial (T–S) resolution. However, the lack of a unified evaluation standard regarding the grid model, T–S resolution and evaluation period leads to inaccurate PDOP evaluation results and unreasonable comparisons among multi-GNSS. We propose the Equal-Arc-Length Grid (GRID_EAL) for PDOP evaluation, which can avoid the bias caused by uneven point distribution present in the commonly used Equal-Interval of Longitude and Latitude Grid (GRID_ELL) and provide more accurate results. Based on GRID_EAL, we thoroughly analyze the varying characteristics and convergence of PDOP metrics with different T–S resolutions. The results indicate that the optimal T–S resolution is 300 s and 3 degrees, reducing time and memory costs by 90% compared to the T–S resolution of 30 s and 3 degrees, while ensuring evaluation accuracy. Moreover, to ensure the representativity of PDOP evaluation for each system, a sliding window method is developed based on the Constellation Ground Track Repeat Period, which enables continuous daily comparisons among multi-GNSS. The proposed method satisfies the requirements for the unified evaluation standard set by the International Committee on Global Navigation Satellite Systems, International GNSS Monitoring and Assessment, and benefits PDOP evaluation and comparison for multi-GNSS.