- Executive Title: "Photogrammetry: Turning Photographs into Accurate 3D Models for Structural Engineering Surveying and Inspection"
- Subtopic (Technical/Focus): "Photogrammetry Techniques and Tools: Creating a Structural Digital Twin with Photographs"
- Engaging Title: "Looking at Structures in a New Light: How to Survey Damage with 3D Models from Photographs?"
This content describes the technique of Photogrammetry , which is a method used to create a highly accurate 3D model from a set of photographs, with an emphasis on its application in surveying and inspecting engineering structures:
2.1. Basic concepts of Photogrammetry
- Definition: $\text{Photogrammetry}$It is the science and technology of measuring geometric values from photographs to create 3D models, maps or measure distances.
- Working principle:
- Take photos of objects or structures from multiple perspectives and with enough overlap.
- The software will process by identifying tie points in the overlapping images.
- Calculate the 3D position of those points and create$\text{Point Cloud}$(group of 3D points)
- convert$\text{Point Cloud}$It is a mesh model ($\text{Mesh Model}$) and add texture from real photos.
- High accuracy: Models can be created with millimeter or centimeter resolution.
- Speed: Data collection is fast (just take a photo) and processing can be done automatically.
- Safe: No need to directly access dangerous areas, drones can be used for photography.
- Reduced costs: Overall, it is lower in cost than traditional surveys (e.g., using laser scanners).
- Permanent record: Photographs and 3D models are permanent records that can be reviewed later.
2.3. Equipment and tools used
- Digital Camera: Camera$\text{DSLR}$, Mirrorless cameras or even high-quality smartphone cameras
- Drone ($\text{UAVs/Drones}$): Used for photographing large structures, tall buildings, or hard-to-reach areas.
- Photogrammetry software:
- Commercial: $\text{Agisoft Metashape}$, $\text{Pix4Dmapper}$,$\text{RealityCapture}$
- Open source: $\text{Meshroom}$,$\text{OpenSfM}$
- High-performance computing: for massive image processing
2.4. Application in surveying and inspecting engineering structures
- Creation$\text{As-Built Model}$: Create a 3D model of the completed structure to compare with the blueprints.
- Damage inspection:
- Cracks: Identify the location, size, and length of cracks on the surface.
- Deformations: Check for settlement, buckling, or distortion of the structure compared to the reference model.
- Corrosion: Assess the area and level of corrosion.
- Construction Quality Inspection: Comparison with Model$\text{BIM}$To find the discrepancy
- Maintenance Planning: Use 3D models to plan access and repairs.
Core Technology:
- $\text{Photogrammetry}$, 3D modeling,$\text{Point Cloud}$,$\text{Digital Twin}$,$\text{3D Modeling}$
Equipment:
- Drone ($\text{UAV/Drone}$), camera,$\text{Photogrammetry Software}$
Engineering Application:
- Structural survey, structural inspection,$\text{As-Built Model}$, Civil Engineering, Maintenance Engineering
Inspection Goal:
- Accuracy measurement, crack detection ($\text{Cracks}$), Deformation detection ($\text{Deformation}$), corrosion inspection
Features:
- High accuracy, permanent data recording, access to hazardous areas
