1. Project Background
Establishing digital archives for historic buildings plays a crucial role in cultural heritage protection. High-precision 3D models generated through oblique photogrammetry provide reliable baseline data for conservation planning and structural analysis.
These detailed digital records allow researchers, engineers, and conservation experts to study architectural structures remotely and repeatedly without physically interfering with the site. When restoration work becomes necessary, the digital model can serve as an accurate reference.
A well-known example is the restoration of Notre-Dame Cathedral in Paris, where highly detailed digital models created before the fire provided essential reference data for reconstruction.
For Jiayuguan, building a protective digital archive not only supports heritage conservation but also enhances tourism promotion. Realistic 3D models can help showcase the site online and attract more visitors.
2. Scenic Site Overview and Model Presentation
The Jiayuguan area typically experiences clear weather conditions in October, with strong sunlight and minimal cloud cover. The slightly warm tone of the sunlight gives the architecture a distinctive golden appearance.
Jiayuguan Pass has a perimeter of approximately 733 meters. A well once stood in the center of the fortress, previously covered by a pavilion that no longer exists.
Outside the western gate stands an additional convex-shaped defensive wall forming a “luocheng” outer enclosure, known as the outer city.
The outer wall is 2.7 meters higher than the inner city wall. The main gate of the outer city bears the inscription “Jiayuguan.” Above the gate is a tower aligned with the east and west towers.
Within the eastern barbican are historical buildings such as:
- Wenchang Pavilion
- Guandi Temple
- Traditional opera stage
Inside the fortress, near the northern side, stands the Guerrilla WarfareGovernment Office, all of which are structures dating back to the Qing Dynasty.
The inner city forms the core of the fortress:
- Perimeter: 640 meters
- Area: 25,000 m²
- Wall height: 10.7 meters
The walls are primarily constructed from rammed earth, with brick reinforcement on the western side, making the structure strong and imposing.
The inner city has two main gates:
- Guanghua Gate (East Gate)
- Rouyuan Gate (West Gate)
The names symbolize governance through harmony and stability along the western frontier.
Each gate is protected by a barbican. Gate towers feature three-story structures with overhanging roofs. At the four corners of the fortress stand corner towers, while the north and south walls include defensive towers.
3. Project Implementation
3.1 Equipment Selection and Ground Control Points
The survey area covered approximately 0.1 km², with an elevation difference of around 20 meters. The tallest buildings reach approximately 30 meters.
The complex layout of towers and fortress walls created challenges for flight planning and accurate 3D reconstruction.
Additionally, strong winds persisted throughout the day, with average wind speeds between 8–10 m/s, affecting UAV flight stability.
To complete the survey:
- Drone platform: DJI M300 RTK
- Camera: Riebo R10Pro oblique photogrammetry camera
A total of 9 ground control points (GCPs) were deployed across the site. Red tape markers shaped as L-targets were used to improve visibility in aerial imagery.
The coordinate system adopted was:
- CGCS2000 coordinate system
- 1985 national elevation datum
Each control point was measured multiple times using RTK equipment to obtain averaged coordinates and ensure measurement accuracy.
3.2 Flight Route Planning
The first step was to design a full-coverage circular flight route using the Riebo flight planning software Rainpoo Route Assistant. This initial flight generated a rough 3D model of the entire site.
The rough model was then used as a reference to design facade flight routes for capturing building sides and architectural details.
Because the ancient structures include complex features such as:
- multi-layered roofs
- extended eaves
- open architectural facades
multiple concentric orbit flights were required to capture the structures from different angles and achieve complete model reconstruction.
Due to the dense arrangement of buildings—such as the Guandi Temple and opera stage—some structures blocked each other’s view during automated flight. Therefore, manual supplementary flights were conducted to capture missing data.
4. Project Results and Summary
During data acquisition:
- 14 UAV flights were conducted
- Approximately 5,000 aerial images were captured
All data were processed in Smart3D for aerial triangulation and full 3D reconstruction.
After the model was generated, the accuracy was verified using the ground control points embedded in the model.
The results confirmed that the model achieved high geometric accuracy and detailed texture quality, meeting the requirements for cultural heritage documentation and digital archiving.
The Riebo R10Pro camera played a key role in achieving these results. It features:
- 100-megapixel medium-format CMOS sensor
- Riebo self-developed MLE optical lens
- Riebo MS high-precision shutter
These components enable the capture of high-resolution, high-sharpness, and low-distortion aerial images, ensuring excellent reconstruction quality for complex architectural structures.
Conclusion
This project demonstrates how UAV-based oblique photogrammetry can efficiently produce high-precision 3D models of historical architecture. The technology provides reliable digital records for cultural heritage conservation, restoration planning, and tourism promotion.
By combining advanced UAV platforms with high-resolution mapping cameras, heritage sites like Jiayuguan can be digitally preserved and studied in unprecedented detail.
