Abstract
Abstract. The accuracy of 3D surface reconstruction was compared from image sets of a Metric Test Object taken in an illumination dome by two methods: photometric stereo and improved structure-from-motion (SfM), using point cloud data from a 3D colour laser scanner as the reference. Metrics included pointwise height differences over the digital elevation model (DEM), and 3D Euclidean differences between corresponding points. The enhancement of spatial detail was investigated by blending high frequency detail from photometric normals, after a Poisson surface reconstruction, with low frequency detail from a DEM derived from SfM.
Highlights
The technology of non-contact optical surface recording is well suited to conservation documentation and complements analytical imaging techniques in heritage science
A cross-section through the ‘gap gauge’, the vertical structure in the centre of the Metric Test Object, shows the additional high frequency detail derived from the photometric normals, compared with the digital elevation model (DEM) derived from the dense matcher and a slice of the point cloud from the Arius laser scanner (Fig. 17)
This study has shown that it is possible to make a reasonable 3D reconstruction of a test object, from a single camera at a fixed viewpoint in an illumination dome, by taking a series of images while systematically translating and tilting the object within the field of view
Summary
The technology of non-contact optical surface recording is well suited to conservation documentation and complements analytical imaging techniques in heritage science. Professional 3D recording technology is capable of extremely high quality metric outputs, but there are currently no applicable guidelines for evaluation of 3D colour digital data suited to the needs of heritage users This indicates the need for a suitable test object and associated protocol to verify recording capabilities and the resulting 3D image quality. Luhmann (2011) identified parameters as physical representation of object surface, orientation strategies, image processing of homologue features and representation of object or workpiece coordinate systems and object scale He discussed strategies for obtaining highest accuracy in object space for state-of-the-art in high accuracy close-range photogrammetry for technical applications. Reconstruction; (b) the test object, made of shiny elements on a dark planar surface, is very challenging for photogrammetry (Toschi et al, 2015); (c) because of the particular acquisition geometry, with the camera fixed in the dome and lens aperture f/8, the depth of field was rather limited and, the images were not uniformly sharp. The object width in the images was 2384 pixels, so the spatial resolution on its baseplate was 10.14 pixels/mm
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