The structure and operation of multi-frequency satellite positioning systems (Multi-Frequency GPS) and the analysis of errors affecting positioning accuracy

The Global Positioning System (GPS) plays a crucial role as a cornerstone of modern navigation and positioning technologies, serving diverse applications such as precise surveying, vehicle tracking, intelligent transportation systems, precision agriculture, and autonomous operations. However, the accuracy of single-frequency GPS receivers is significantly affected by several error sources, including ionospheric and tropospheric delays, multipath interference, satellite and receiver clock biases, and hardware noise. The advent of multi-frequency GPS receivers provides an effective approach to mitigate these limitations and enhance positioning precision. In multi-frequency systems, simultaneous utilization of signals transmitted on multiple bands-such as L۱ (۱۵۷۵.۴۲ MHz), L۲ (۱۲۲۷.۶۰ MHz), and L۵ (۱۱۷۶.۴۵ MHz)-allows accurate modeling of ionospheric propagation effects and substantial elimination of frequency-dependent delays. Moreover, the integration of carrier phase and pseudorange measurements enables centimeter-level accuracy, which is essential for high-precision applications like Real-Time Kinematic (RTK), Precise Point Positioning (PPP), and autonomous navigation. This study examines the structural design of multi-frequency GPS signals, receiver architecture, and mathematical positioning models, while analyzing the dominant error sources and their compensation methods. It further highlights the performance benefits achieved through multi-frequency combinations in real-world scenarios such as unmanned aerial vehicle (UAV) operations, intelligent transport systems, and geodynamic monitoring. The findings demonstrate that the adoption of multi-frequency GPS not only effectively mitigates atmospheric and geometric errors but also paves the way toward the evolution of next-generation satellite-based positioning and navigation systems.

کلیدواژه ها:

Multi-frequency GPS ، GNSS ، satellite positioning ، error analysis ، carrier-phase processing ، positioning accuracy