How UAV Oblique Photography Transforms 3D Modeling for Smart Cities

Background

UAV‑based oblique photogrammetry provides low‑cost, high‑efficiency 3D reconstruction of real‑world scenes and is widely used in urban planning, public security, tourism, environmental protection, and agriculture.

Technical Process

1. Field Photography (External Capture)

Plan flight lines, fly the UAV along them, and capture overlapping oblique images.

After acquisition, process the images to generate a 3D model and perform internal data checks; re‑acquire if necessary.

1.1 Control Point Selection

At least five high‑grade planar control points are required within the survey area. Points must be placed in well‑visible, unobstructed locations, inside the overlapping region of adjacent flight strips, no more than 3 cm from the strip centreline and at least 1.5 cm from image edges.

1.2 Control Point Measurement

Measurements are performed with GPS achieving ±10 mm + 2 ppm horizontal and ±20 mm + 2 ppm vertical accuracy. Each point is observed for at least 15 seconds, twice, after a stable RTK fix is obtained. The final coordinate is the average of the two observations, recorded to 0.001 m.

1.3 Flight and Imaging Equipment

Select UAVs based on payload capacity, platform type (multirotor or fixed‑wing), and mission requirements. Use high‑resolution cameras or multi‑camera rigs to ensure sufficient overlap and image quality for 3D reconstruction.

2. 3D Modeling

2.1 Aerial Triangulation

Aerial triangulation refines the sparse point cloud and provides absolute orientation. Two approaches are used: simulated and analytical triangulation.

2.2 Densification (Point Cloud Generation)

Software such as Smart3D Capture Master generates dense point clouds from the triangulation results, enabling high‑detail 3D reconstruction.

2.3 Model Reconstruction and Block Processing

Because data volumes are large, the model is divided into blocks for parallel processing. After block reconstruction, the pieces are merged into a seamless 3D model.

3. Internal Data Processing and Quality Check

Processing is performed on an EPS GIS workstation, integrating CAD and GIS techniques to produce a unified data model. The workflow includes environment preparation, EPS file creation, model import, DOM import, stereoscopic editing, data inspection, and final output.

Technical Trends

Advances in UAV technology, high‑resolution imaging, and artificial intelligence (e.g., neural radiance fields) are accelerating and refining 3D reconstruction, expanding applications in emergency response, tourism, and environmental monitoring.

References

CH/Z 3001-2010, UAV Flight Safety Requirements

CH/Z 3002-2010, UAV System Technical Requirements

CH/Z 3003-2010, Low‑Altitude Digital Aerial Photogrammetry Internal Standards

CH/Z 3005-2010, Low‑Altitude Digital Aerial Photography Standards

CH/Z 8021-2010, Digital Aerial Camera Calibration Procedures

Beidou Satellite Navigation System Interface Specification

GB/T 20257.1-2007, National Basic Scale Map Symbols Part 1

GBT 20257-2007, Scale Map Symbol Standards