**Summary**
Topographic surveying is a complex and systematic process that has traditionally relied on aerial photogrammetry. However, conventional aerial photography systems are expensive, require strict weather conditions, and involve high operational demands, making them unsuitable for rapid or large-scale applications. In contrast, UAV-based aerial photography systems offer flexibility, efficiency, and cost-effectiveness, making them an ideal alternative. This paper presents a case study of a topographic survey conducted in an open-pit mine in Inner Mongolia using the Sirius free image-controlled drone system. The project successfully generated DOM, DEM, and point cloud data without ground control points, achieving high accuracy suitable for large-scale mapping in complex terrains. The results demonstrate the potential of UAVs to revolutionize traditional surveying methods, especially in areas where manual access is difficult.
**Introduction**
With China's rapid economic growth, topographic mapping has evolved from manual methods to advanced aerial techniques. Traditional aerial photography faces challenges such as high costs, limited weather windows, and difficulty in accessing remote areas. Drone-based aerial systems, however, have emerged as a flexible and efficient solution. This paper explores the application of the Sirius UAV system in a mining area in Inner Mongolia, where it was used to produce high-precision topographic data without the need for ground control points. The study highlights how modern UAV technology can meet the demands of complex terrain surveys, offering a reliable and cost-effective alternative to traditional methods.
**1. Technical Advantages of the Sirius UAV Aerial Photography System**
**1.1 Built-in High-Frequency RTK Module for Image-Free Surveying**
Traditional aerial surveys require extensive ground control points, which are time-consuming and resource-intensive. In contrast, the Sirius UAV system uses a high-frequency RTK module to provide real-time positioning during flight. This eliminates the need for ground control points and ensures accurate orientation for each image. The system’s ability to maintain precise POS (Position and Orientation System) information allows for high-accuracy mapping even in challenging environments.
**1.2 MAVinci Desktop for Intelligent Flight Planning**
MAVinci Desktop enables users to plan flights based on the survey area, automatically adjusting altitude and overlap rates according to terrain variations. This ensures optimal image quality and safety while significantly reducing planning time. Operators can quickly simulate and adjust flight paths, making the entire process more efficient and user-friendly.
**1.3 AgiSoft PhotoScan Pro for Automated Data Processing**
The AgiSoft PhotoScan Pro software allows for fully automated processing of aerial images, producing high-resolution orthophotos, DEMs, and point clouds without manual calibration. This makes the system accessible to non-experts and greatly speeds up data generation. In one case, 1,460 images were processed in just 12 hours, resulting in accurate topographic data within a short timeframe.
**2. Engineering Implementation**
**2.1 Project Overview and Flight Parameters**
The project aimed to create a high-precision digital elevation model for earthwork calculations in a mining area in Bayannaoer, Inner Mongolia. The survey covered an area of 4.6 km² with significant elevation changes. Due to the rugged terrain, traditional methods would have been impractical. The Sirius UAV system was chosen for its ability to operate efficiently in such conditions.
**2.2 Workflow of UAV Aerial Survey**
The entire workflow—from route design to image stitching—was completed using MAVinci Desktop. AgiSoft PhotoScan Pro then generated DOM, DEM, and point cloud data, which were further processed using Global Mapper and EPS software. This streamlined approach reduced both time and labor requirements.
**2.3 Detection Points and Accuracy Evaluation**
To assess accuracy, detection targets were placed across the survey area. These targets were measured using RTK GPS to ensure precision. The results showed that the UAV system met the required accuracy standards for both plane and elevation measurements, proving its reliability for large-scale topographic surveys.
**3. Accuracy Analysis of Topographic Surveys**
The elevation accuracy of the generated DEM was evaluated against industry standards. The maximum error was found to be 0.362 meters, well within the allowable limit of 0.25 meters. This confirms that the UAV system can produce high-quality topographic maps suitable for engineering projects in complex terrains.
**4. Conclusion**
This case study demonstrates the effectiveness of UAV-based aerial photography in complex terrains. The Sirius system offers a practical, cost-effective, and efficient solution for topographic mapping, especially in areas where traditional methods are impractical. Its integration of advanced software and hardware makes it an ideal tool for modern surveying. As drone technology continues to evolve, it will play an increasingly important role in geospatial data collection, transforming the way we map and measure our world.
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