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AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF
THERMOGRAPHIC DIGITAL TERRAIN MODELS
S. Lagüela, L. Díaz-Vilariño, D. Roca, J. Armesto
Applied Geotechnologies Research Group, University of Vigo (Spain)
Corresponding Author: susiminas@uvigo.es
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
THERMOGRAPHIC INSPECTIONS IN
BUILDINGS
CLOSE RANGE AERIAL THERMOGRAPHY
THERMOGRAPHIC AERIAL ACQUISITIONS
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
OBJECTIVE:
Extension of the accurate thermographic studies performed in three-dimensions for buildings
to medium size areas (neighbourhoods, districts, villages) using a low-cost aerial platform
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
Okto XL by Mikrokopter
• 2 kilograms payload
• 20 min flight autonomy
Gobi384 by Xenics with 10mm lens
• 384x288 UFPA
• 50 fps data acquisition
• 500 grams (lens included)
> NO LIMITS TO COPTER SPEED
> NOT EXCEEDING COPTER PAYLOAD
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
FLIGHT CONSIDERATIONS:
• AREA COVERED: 8760 m2
• FIELD OF VIEW OF THE CAMERA: 50ºx40º
• OVERLAP BETWEEN STRIPS: 50%
FLIGHT PARAMETERS:
• FLIGHT HEIGHT: 50 meters
• NUMBER OF STRIPS: 4
• FLIGHT SPEED: 5 m/s
5 minutes flight
14000 thermographies
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
DISTORTION CORRECTION
•CAMERA CALIBRATION
IMAGE REGISTRATION
•TIE POINTS BETWEEN THERMOGRAPHIES
•CORRELATION VALUE
•PROPRIETARY SOFTWARE
OVERLAPPING AREA CALCULATION
•AVOID EDGE SEAM
•LINEAR TRANSITION METHOD
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
1. DISTORTION CORRECTION
> Remove RADIAL DISTORTION introduced by the camera
> CAMERA: high distortion coefficients due to the SMALL FOCAL LENGTH of the lens (10mm)
> Camera calibrated with a CALIBRATION FIELD BASED ON EMISSIVITY DIFFERENCES
PRIOR CORRECTION POST CORRECTION
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
1. DISTORTION CORRECTION
> CAMERA: high distortion coefficients due to the SMALL FOCAL LENGTH of the lens (10mm)
CALIBRATION PARAMETER VALUE
Pixel size (mm/pix) 0,0156
Format size (mm) 5,9997 (W) * 4,5000 (H)
Principal point (mm) Xp 2,8807
Yp 2,2891
Radial distortion K1 -0,1142
K2 2,924 e-3
K3 0
Tangential distortion Px -1,813 e-4
Py -9,998 e-5
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
2. IMAGE REGISTRATION
•TIE POINTS BETWEEN THERMOGRAPHIES
•CORRELATION VALUE
•PROPRIETARY SOFTWARE
Manual marking of tie points: 4 per thermography
Computation of the CORRELATION VALUE: refine tie points position
REGISTERED IMAGE
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
3. OVERLAPPING AREA CALCULATION
•AVOID EDGE SEAM
•LINEAR TRANSITION METHOD Computation of OVERLAPPING AREA depending on its position in each thermography:
𝑀𝑖 =𝑋𝑚𝑎𝑥 − 𝑋𝑖
𝑋𝑚𝑎𝑥 − 𝑋𝑚𝑖𝑛∙ 𝐴𝑖 + 1 −
𝑋𝑚𝑎𝑥 − 𝑋𝑖
𝑋𝑚𝑎𝑥 − 𝑋𝑚𝑖𝑛∙ 𝐵𝑖
Image A Image B Image M
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
THERMOGRAPHIC DIGITAL TERRAIN MODEL
DIGITAL TERRAIN MODEL
THERMOGRAPHIC + VISIBLE FUSION
ORTHOIMAGE
Georeferencing through the coordinates of CONTROL POINTS
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
THERMOGRAPHIC DIGITAL TERRAIN MODEL
INFORMATION ABOUT ELEMENTS ON THE GROUND GEOMETRIC INFORMATION ABOUT THE SURFACE
CLASSIFICATION ON LAND USES
DEPENDING ON THEIR TEMPERATUREAREAS AND DISTANCES
CALCULATION
1 2
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
LAND USES DEPENDING ON THEIR TEMPERATURE
PIXEL SEGMENTATION > Conversion of the image from RGB color space to XYZ color space
> Classification according to X-Z values (chromaticity)
> Removal of incorrectly classified pixels (colour value threshold)
Cluster 1 Cluster 2 Cluster 3
1
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
AREAS CALCULATION - pixel size: 25cm
Cluster 1
Low Vegetation (grass)
211840 pixels
13240 m2
Cluster 2
Tall Vegetation (bushes, trees)
128800 pixels
8050 m2
Cluster 3
Metal Roofs
74400 pixels
4650 m2
2
< 5% error
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
- METHODOLOGY FOR THE GENERATION OF A THERMOGRAPHIC DIGITAL TERRAIN MODEL
- Using a LOW-COST AERIAL PLATFORM (copter type)
- Allowing the performance of analysis:
- THERMOGRAPHY: classification of land uses
detection of building prints
detection of faults in roofs
- GEOMETRY: quantification of forest masses
surface calculation per land use
calculation of heat losses of buildings
- Verification of surfaces with reality using NATIONAL CARTOGRAPHY
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
- FUTURE WORK:
EXPLOITATION OF THE THERMOGRAPHIC DIGITAL TERRAIN MODEL
- Extraction of parameters of interest:
- Coordinates of BUILDINGS
- Evaluation of HEAT ISLANDS
- Identification of TREE SPECIES
- Detection of BURIED OBJECTS
INTRODUCTION DATA ACQUISITION
• EQUIPMENT
DATA ACQUISITION
• FLIGHT
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC MOSAIC
THERMOGRAPHIC DTM GENERATION
• THERMOGRAPHIC DTM TEXTURIZATION
RESULTS AND DISCUSSION
• LAND USES
CONCLUSIONS
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF THERMOGRAPHIC DIGITAL TERRAIN MODELS
- REFERENCES:
1. S. Lagüela, H. González-Jorge, J. Armesto, J. Herráez, High performance grid for the metric calibration of thermographic
cameras, Measurement Science and Technology, 23(1), 2012, 9pp.
2. S. Lagüela, J. Armesto, P. Arias, J. Herráez, Automation of thermographic 3D modelling through image fusión and
image matching techniques”, Automation in Construction, 27, 24-31, 2012.
3. CIE, Colorimetry. CIE Publication 15.2, 2nd Ed, 1986, 19-20, 56-58.
4. Wiki Mikrokopter: www.mikrokopter.de
AERIAL THERMOGRAPHY FROM LOW-COST UAV FOR THE GENERATION OF
THERMOGRAPHIC DIGITAL TERRAIN MODELS
S. Lagüela, L. Díaz-Vilariño, D. Roca, J. Armesto
Applied Geotechnologies Research Group, University of Vigo (Spain)
Corresponding Author: susiminas@uvigo.es