Abstract: With the rapid development of the low-altitude economy， the importance of leveraging terrestrial 5th Generation （5G） networks to provide wide-area and reliable wireless coverage for low-altitude users， such as Unmanned Aerial Vehicles （UAVs）， has become increasingly important. However， this approach faces numerous challenges， including signal blind spots in low-altitude areas caused by the sidelobe coverage of terrestrial base station antennas， and a complex， spatially heterogeneous interference field resulting from the open-channel environment. Consequently， conventional measurement methods struggle to accurately characterize the true channel conditions. To address these issues， this study designed and implemented an anti-interference low-altitude radio mapping system for 5G networks. A multi-base station signal analysis method based on time-domain joint modeling and estimation was developed. This method， under a Maximum Likelihood Estimation （MLE） framework， leverages the prior knowledge of shared physical parameters among multiple beams from the same base station and incorporates an iterative Successive Interference Cancellation （SIC） framework. This significantly enhances the accuracy when detecting weak signals and estimating parameters in dense environments with strong interference. Systematically， a lightweight signal acquisition platform centered around a UAV and a software radio was developed， and a dual-process asynchronous processing software architecture based on shared memory was designed. This architecture effectively decouples the stringent real-time task of data reception from the non-deterministic task of data storage. Through efficient inter-process communication， it achieves the lossless and continuous acquisition of high-speed In-phase/Quadrature （I/Q） data on a lightweight airborne computing platform. Deployment and field measurements in a real urban environment demonstrated that the proposed system and algorithms have significant advantages over baseline solutions in terms of weak signal detection sensitivity， multi-beam resolution capability， and the completeness of the constructed radio map. This research provides an effective technical solution for characterizing the 5G low-altitude electromagnetic environment， and its mapping results can offer crucial data support for subsequent network-side 3D coverage optimization and terminal-side communication-aware path planning.