Abstract: This paper addresses the challenges of large-scale,high-precision,and efficient railway surveying in complex mountainous areas characterized by high altitude,significant elevation differences,extreme cold and oxygen deficiency,and conducts research on the comprehensive integration and innovative application of surveying technologies.The technical key points of the air,space and ground surveying methods and their applicability at each stages of railway surveying are systematically summarized.Furthermore,a space-air-ground integrated comprehensive surveying system suitable for complex mountainous areas is established.This system has been successfully applied in railway projects such as the Sichuan-Xizang and Yunnan-Xizang lines,generating a variety of surveying outcomes including multi-scale topographic maps,surface deformation rate maps,real-scene 3D models,large-scale stereoscopic image models,digital elevation models,route centerlines,cross and longitudinal sections,and control networks,etc.It significantly improves the quality and efficiency of surveying,providing important technical references and practical experience for railway surveying in similar challenging environments.

Key words: space-air-ground integration, satellite remote sensing, oblique photography, LiDAR, UAV