7/2/2023 0 Comments Meshlab icp![]() Point cloud data was imported into Meshlab using the function to download directly from Photosynth's online service. The site was divided into overlapping segments for SFM processing and the resulting point clouds meshed and combined using Meshlab, a tool developed with the support of the 3D-CoForm project. 3.2.2 Meshing Photosynth point cloud data While point clouds derived from Photosynth are sparse compared with other solutions, the resulting mesh was of suitable density for the purpose of the animated outcome. 2012) and would be considered for future projects with similar demands. Agisoft Photoscan in particular has emerged as a valuable and versatile tool for site visualisation (see Verhoeven et al. Ideally, more structured photographs would be used in conjunction with software solutions that offered more overall control and flexibility. While Autodesk 123D Catch was also considered (both solutions use cloud computing rather than processing locally), Photosynth was found to be more forgiving in that it was able to resolve images from erratic relative camera positions. Images © Kieran Baxter (CC BY-NC-ND 3.0)ĭue to the high number of photographs gathered and the unstructured nature of the camera positions, Microsoft Photosynth was used to derive the necessary point cloud data. Figure 7a and 7b: Two photographs from the pole-mounted camera. The area adjacent to the sea wall, consisting of the broch, Iron Age wheelhouses and Laird's House, was particularly complex and restrictive to move around (Figure 7). Instead image sequences were taken along a series of paths that aimed to cover the entire surface of the site, including the sides of upstanding structures. The pole-mounted camera was limited to areas that could be accessed on foot, making it impossible to traverse the site in a conventional grid pattern. The sequences of photographs taken from the pole-mounted camera resulted in thousands of photographs positioned approximately 6m above the surface of the site (Figure 6). 3.2.1 Gathering photographs using a pole-mounted camera Figure 6: Operating the pole-mounted camera. ![]() ![]() This section of the article describes how these challenges were overcome using a combination of image-gathering hardware and image-processing software. A workflow was adopted to achieve this on a low budget, with limited access to low altitude aerial photography on site. The mesh generated for 'Jarlshof' was not intended as a tool for survey or analysis but was required to provide an accurate framework on which photo-textures could be projected. The flexibility and accuracy of these methods make them a highly viable tool for archaeological mapping and spatial analysis (Verhoeven et al. In recent years the combined use of low altitude aerial photography and SFM photogrammetry has emerged as a cost-efficient method for survey and modelling (Remondino et al. The first stage in production was the creation of a structural mesh of the site, which would form a basis for all of the animated sequences. PREVIOUS NEXT CONTENTS ISSUE HOME 3.2 Structure from motion photogrammetry
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