A presentation given at the Global Bamboo and Rattan Congress (BARC 2018), 25-27 June 2018.

1. Image- based 3d reconstruction of bamboo-steel spatial
truss structure using mini UAV
Candela G., Barrile V.
Geomatics Laboratory, Department of Civil, Energy, Environmental and Materials engineering
Mediterranea University, Reggio Calabria, Italy, 89128 Reggio Calabria
Demartino C., Monti G.
Nanjing Tech University, Nanjing, Jiangsu, 211816 China

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1 | Structure overview
Located in Nanjing Tech University, College of Civil Engineering
Ø Spatial truss for roof system
Ø Structural materials:
Bamboo (GluBam) and steel
Ø Built in 2016

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1 | Structure overview
Bamboo-steel spatial truss
Front view Left view

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Truss module:
1 | Structure overview
Bamboo-steel spatial truss
Cross-section:

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2 | Survey techniques and aerial survey
3d survey techniques: aerial survey
UAV model:
• Dji Mavic Pro
• Satellite Positioning Systems: GPS/Glonass
• Weight: 734 gr
• Flight time: 27 min
• Sensor: CMOS
• Effective pixels: 12.35 M
• 3 axis gimbal
• Cost = 1500 € (13.000 Yuan)
Aero-photogrammetry:
Structure from Motion (SFM) algorithm
• Camera poses estimation from images and camera
characteristics
• Scene reconstruction through «point cloud»
Main advantages:
+ Cheap and fast methodology
+ Extraction of geometrial characteristics
+ Photographic dataset for inspections

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Dataset:
Photos: 459
Dataset GB: 2,5 gb
Image resolution: 4000*3000
Camera settings: 1/23’’ CMOS
GPS coordinate: yes
Survey time: 30 minutes
3 | Aerial survey of Bamboo spatial truss structure
Methodology and workflow
Ø Ground Sampling Distance calculation (for images): 0,31 cm/pixel
Ø Set of flight acquisition plan: 80% overlap both vertical and horizontal

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Ø Image acquisition through UAV
Ø Sparse point cloud construction
Ø Dense point cloud construction
Ø Noise reduction, dense point cloud cleaning
Sparse point cloud: 34.500 points
Running time: 21 min
3 | Aerial survey of Bamboo spatial truss structure
Methodology and workflow
Ø Object recognition from images: Scale
Invariant Feature Transform (SIFT)
Ø 3d reconstruction algorithm SFM
Dense point cloud: 3 million points
Running time: 5h
Ø Camera poses estimation

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Front view Left view
Right view
3 | Aerial survey of Bamboo spatial truss structure
Methodology and workflow
Ø 3d mesh: 839.405 points, 1.674.921
triangles
Running time: 1h

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Top view
3 | Aerial survey of Bamboo spatial truss structure
Methodology and workflow
Mesh to Surface: simple geometry reconstruction
Extraction of geometrical features

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4 | Results and conclusions
3d reconstruction
Real and reconstructed model
Cross section
Real = 5.6 cm
From reconstruction = 5.8 cm
Top view
Real = 0.84 m
From reconstruction = 0.85 cm

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4 | Results and conclusions
Dataset for inspection and maintainance
Mold