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Abstract: The rapid expansion of the low-altitude economy is driving strong demand for highly accurate and reliable positioning technologies to support diverse aerial operations. This review examines core positioning methodologies within the low-altitude intelligent network (LAIN) framework, beginning with an analysis of positioning requirements and performance metrics for low-altitude flight scenarios. It systematically assesses the principles, strengths,and limitations of mainstream positioning systems, including Global Navigation Satellite Systems (GNSS), terrestrial wireless positioning, and autonomous navigation, and it surveys prevalent integrated and cooperative positioning schemes. Our analysis demonstrates that standalone positioning technologies are inadequate in complex low-altitude settings, underscoring the pivotal role of multi-source fusion and unmanned aerial vehicle (UAV) swarm cooperative positioning as future trends. To address infrastructure gaps and high deployment costs in current LAIN systems, we propose a "space?air?ground" integrated and cooperative positioning architecture centered on GNSS and the 5th generation mobile communication technology (5G). The ground layer integrates 5G and GNSS for wide-area enhanced positioning. The aerial layer uses 5G aircraft-to-everything (A2X) and sidelink (SL) communications to build self-organizing networks for cooperative UAV localization. The space layer leverages low Earth orbit (LEO) satellites to overcome coverage limitations in communication and positioning. This hierarchical architecture reduces deployment costs through infrastructure reuse and enables deep integration of communication and navigation capabilities. By supporting collaborative enhancement across all three domains, the framework improves positioning robustness and delivers cost-effective, ubiquitous, and highly reliable positioning services. Finally, we outline promising research directions.This review aims to provide a systematic reference and a novel architectural perspective for the ongoing development of LAIN.