## 1 Introduction
Although it can acquire high-precision data, the instrument should be repeatedly moved for scanning, as some areas are not easily accessible by the laser. The periodic analysis of the amount of geomorphic change may lead to reduced model quality and may introduce various errors, thus resulting in significant differences in analysis results and associated challenges [28]. The UAV-based airborne LiDAR (ALS) technology can provide more detailed 3D surface models [29]. [PERSON] et al. [30] used ALS to identify lithological and geomorphological processes in large-scale valley areas for engineering geological mapping. [PERSON] et al. [31] analyzed the secondary debris flow disaster chain caused by landslides using the high-resolution DEM from the airborne LiDAR. [PERSON] et al. [32] acquired fault cliffs and fault-related geomorphological data, extracted semi-automatic fault zone features, and conducted feature analysis. High-resolution DEMs have been extensively used in various geomorphological surveys and analyses. LiDAR can more flexibly adapt to complex topographic environments and compensate for the inability of optical remote sensing images to truly indicate the ground surface. However, the monolithic and insufficient quality data cannot provide the basic analysis required for high-precision large-area geomorphological feature detection and analysis in highland and mountainous areas with significant vertical drop and a complex topographic environment. The fusion of the UAV-LiDAR technology not only solves the problem of insufficient data quality due to the natural environment but also makes up for the identification and analysis of incomplete geographical features with multi-source data results. UAVs can provide a wide range of comprehensive views from images, generate highly detailed topographic information, rebuild the true shape of the geomorphology [33], optimize conventional survey methods, and increase the efficiency and accuracy of survey results. Additionally, 3D point-cloud data obtained by LiDAR technology can remove the effect of vegetation and can quickly and accurately construct DEMs since climate and vegetation significantly affect the flight position of UAVs, which further affects the accuracy of UAV images and DEMs [34]. High-precision DEMs are capable of collecting very useful information to describe the geomorphology. Moreover, they are critical to facilitating subtle geographical changes and the accurate identification of different geographical types. DEMs take on a certain scientific significance and practical effect in how to more effectively detect the special annular structure of geomorphological data in the mountainous environment of central Yunnan plateau and in the identification and quantitative analysis of geomorphological features from multiple perspectives. In this study, the annular structure geomorphology of the Dinosaur Valley of Lufeng City, Chuxiong, Yunnan was taken as the research area, and the complex pit rim structure was selected as the research object. High-resolution images and high-quality point-cloud data were obtained automatically using the UAV-LiDAR system. The 3D model was constructed using the SfM-MVS technology, and the LiDAR point-cloud was processed to build the high-resolution DEM. High-precision topographic survey data and numerical simulation of 3D topographic scenes were comprehensively utilized. Multi-angle, qualitative, and quantitative geographical feature was identified, measured, and analyzed through visual interpretation, DEM visualization, GIS topographical feature extraction, and analysis. Furthermore, efficient and high-quality technology and methods were provided in this study.