## 1 Introduction  
Mineral resources are the basic energy source and important raw materials in China. With the development of the national economy, the demand for mineral resources is rising, and mining depth and intensity are growing. Underground mine roadways, an important channel for mining ores, are the key link to ensure the safe and efficient extraction of mineral resources. However, long-term, high-intensity, and destructive mining has led to stress redistribution of the rock mass, resulting in continuous deformation and even rock mass failure [1, 2, 3]. Therefore, it is of great significance to map and monitor the underground mine roadways to ensure safe and smooth operation [4, 5]. However, an underground mine's operation space is narrow, the light is insufficient, and there is much dust, which requires the sensor to have a certain degree of penetration. It is difficult to obtain spatial information using traditional surveying techniques such as total stations, leveling instruments, and sonar [6, 7]. A non-contact measurement method, the laser point cloud is suitable for reflecting the characteristics of objects in a variety of special and complex environments. The survey results enable reduction in mining losses and improvement in the design of mining geometry. In addition, the deformation data of the rock mass can be obtained by comparing the point clouds captured at different times, which can provide essential information for safety checks, structural assessments, or predictive maintenance [3]. In recent years, the handheld laser scanning (HLS) system based on simultaneous localization and mapping (SLAM) technology has provided a new opportunity [8, 9, 10, 11]. \"Groundhog\", a mapping robot developed at Carnegie Mellon University, carries scanners, gyroscopes, and other equipment, and uses SLAM technology to construct 3D maps of abandoned mine shafts [12]. [PERSON] et al. developed the ZebRevo mobile 3D laser mapping system. It relies on inertial measurement units (IMUs) and odometers to estimate the system position, while the light detection and ranging (LiDAR) system is used to extract scene features for obtaining point clouds of the underground mine space, which solves the problem of global navigation satellite system (GNSS) los of lock [13]. The GHJS12 mining 3D laser scanner was developed by Longruan and Digital Green Earth Technology Co., Ltd. (Beijing, China), and has been used to classify the point clouds of mine roadways and to construct models of substation chambers and pump rooms [14]. Although handheld mobile laser scanning appears to be the most suitable method for underground mining surveys [15], sufficient scene features are a prerequisite for obtaining the accurate position of the HLS system. In the case of an underground mine, IMU drift is inevitable and point cloud positioning accuracy is poor due to the presence of repetitive features and long periods without loop closure. Static terrestrial laser scanning (TLS) has become one of the most important approaches to obtaining spatial information. It is widely used in various related fields, such as tunnels [16; 17], bridges [18; 19], and dams [20]. Particularly in underground mines, point clouds obtained from terrestrial laser scanning make up for the shortcomings of the HLS system, which are used to identify and mitigate roadway-related hazards. The cavity monitoring system (CMS), cavity auto scanning laser system (C-ALS), and BLSS-PE laser scanner have become effective means of underground mine measurement [21; 22; 23; 24; 25]. However, the TLS system has a short measurement distance and complicated station deployment. Point cloud data is seriously missing in mine shafts and drift engineering with complicated internal structure. As we can see, it is difficult for a single platform to meet the application requirements for all element measurements in an underground mine.