Abstract
Abstract. The aim of this research is the performance evaluation of the termographic cameras for possible use for photogrammetric documentation and deformation analyses caused by moisture and isolation problem of the historical and cultural heritage. To perform geometric calibration of the termographic camera, the 3D test object was designed with 77 control points which were distributed in different depths. For performance evaluation, Flir A320 termographic camera with 320 × 240 pixels and lens with 18 mm focal length was used. The Nikon D3X SLR digital camera with 6048 × 4032 pixels and lens with 20 mm focal length was used as reference for comparison. The size of pixel was 25 μm for the Flir A320 termographic camera and 6 μm for the Nikon D3X SLR digital camera. The digital images of the 3D test object were recorded with the Flir A320 termographic camera and Nikon D3X SLR digital camera and the image coordinate of the control points in the images were measured. The geometric calibration parameters, including the focal length, position of principal points, radial and tangential distortions were determined with introduced additional parameters in bundle block adjustments. The measurement of image coordinates and bundle block adjustments with additional parameters were performed using the PHIDIAS digital photogrammetric system. The bundle block adjustment was repeated with determined calibration parameter for both Flir A320 termographic camera and Nikon D3X SLR digital camera. The obtained standard deviation of measured image coordinates was 9.6 μm and 10.5 μm for Flir A320 termographic camera and 8.3 μm and 7.7 μm for Nikon D3X SLR digital camera. The obtained standard deviation of measured image points in Flir A320 termographic camera images almost same accuracy level with digital camera in comparison with 4 times bigger pixel size. The obtained results from this research, the interior geometry of the termographic cameras and lens distortion was modelled efficiently with proposed approach for geometric calibration.
Highlights
In the recent years, the digital and thermal infrared cameras have provided powerful tools for photogrammetric documentation of cultural and historical buildings, deformation analysis of buildings and bridges in different investigations
The workflow for the performance evaluation of the termographic and digital cameras is presented for possible use for determination of 3D geometric locations of the historical and cultural heritage buildings in photogrammetric documentation and deformation analyses caused by moisture and isolation problem of the historical and cultural heritage
The geometric calibration parameter were determined with introduced additional parameters into the bundle block adjustments for interior orientation parameters (x0, y0, c), radial distortion parameters (K1, K2, K3) and tangential distortion parameters (P1, P2) for both Flir A320 termographic camera and The Nikon D3X SLR digital camera
Summary
The digital and thermal infrared cameras have provided powerful tools for photogrammetric documentation of cultural and historical buildings, deformation analysis of buildings and bridges in different investigations. Digital cameras and thermal imaging systems widely used in modern medical, automotive, industrial, architectural, and military applications. The use of these thermal imaging systems and cameras is increased for documentation of the historical and cultural heritage, 3D modeling, deformation analysis, restoration and conservation applications (Grinzato et al, 2002). The geometric accuracy in photogrammetric documentation, deformation analyses and monitoring studies of historical buildings with termographic cameras mainly related with geometric performance of camera. The performance evaluation of the termographic cameras is aimed for possible use for photogrammetric documentation and deformation analyses caused by moisture and isolation problem in wet areas which was recorded as historical and cultural heritage. The Nikon D3X SLR digital camera was calibrated and used as reference for comparison
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