Coded Target Techniques in Photogrammetric Measurement Systems
Summary
In photogrammetric measurement systems, coded targets are deliberately patterned markers that enable automatic identification and precise localisation within images or image sequences. These markers are designed to resolve correspondence problems between multiple views, improving the efficiency and accuracy of tasks such as camera calibration, three-dimensional reconstruction and deformation monitoring. Typical designs include concentric circles, point distributions and cross-shaped elements, each offering distinct advantages in robustness to perspective distortion, illumination variance and motion blur. The main processing pipeline involves target detection, centre estimation, pattern decoding and coordinate extraction. Recent advances have focused on optimising detection under challenging conditions—such as uneven lighting, oblique viewing angles and platform instability—and on extending the technique to unmanned aerial vehicles and large-scale industrial environments. The global significance of coded targets spans civil engineering, aerospace inspection, cultural heritage documentation and precision manufacturing, where non-contact, high-resolution measurement is essential.
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Coded Target Techniques in Photogrammetric Measurement Systems publication trend
The graph below shows the total number of articles in coded target techniques in photogrammetric measurement systems across all publications each year (not limited to Nature Index journals).
Technical terms
Coded target: An optical marker bearing a machine-readable pattern that encodes a unique identifier and enables automatic point correspondence across images.
Photogrammetry: The science of obtaining reliable measurements and three-dimensional information from photographic images.
Radon transform: A mathematical operation that integrates image intensity along lines at specific angles, used here to detect linear or cross-shaped features.
Homomorphic filtering: A frequency-domain image enhancement technique that separates the illumination component from reflectance to correct uneven lighting.
Affine transformation: A linear mapping that preserves points, straight lines and parallelism, used to normalise target patterns under perspective distortion.
References
- An Adaptive Radon-Transform-Based Marker Detection and Localization Method for Displacement Measurements Using Unmanned Aerial Vehicles. Sensors (2024).
- AHF: An Automatic and Universal Image Preprocessing Algorithm for Circular-Coded Targets Identification in Close-Range Photogrammetry under Complex Illumination Conditions. Remote Sensing (2023).
- A Robust and Effective Identification Method for Point-Distributed Coded Targets in Digital Close-Range Photogrammetry. Remote Sensing (2022).
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