24-5 Best Practices for Hand Sample Photogrammetry in Non-Ideal Environments.

Session: Transforming Geoscience Education: Reimagining how we teach the Earth (Posters)

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Abstract:

      Easily interpretable hand-samples are essential tools for students enrolled in introductory geology courses. However, high-quality samples are not always available due to combinations of accessibility, cost, and fragility. This need was further exacerbated during the Covid-19 pandemic, when virtual education environments were eminent, and physical hand-samples were almost impossible to share. Modern photogrammetry techniques allow for the capture of three-dimensional characteristics of hand samples from two-dimensional media, enabling creation and hosting of digitally manipulable models for use in educational and archival fields. Although this method alleviates the issue of sample access, it is not without challenge. Previous literature extensively covers the use of 3D photogrammetry software and hardware packages in an ideal setting; however, the reality is that achieving perfectly diffuse lighting and balancing contrasts in a laboratory or classroom setting requires more effective methods than previously presented. This research constrained these methods through the development of high-resolution models of igneous samples in rigorous,controlled conditions. The primary goal of this work was to create a set of 3D models of geological hand samples through the use of the Ortery Photocapture 360TM and Agisoft Metashape TM software workflows. The utilization of a Canon EOS Rebel T7 TM DSLR camera and adaptable studio lighting ensured the collection of photographic data while managing image overlap, focus consistency, and exposure. The images were processed through Agisoft Metashape TM using a Structure-from-Motion workflow, allowing for the creation of dense point clouds and subsequent mesh reconstructions based upon two-dimensional image alignment. Technical challenges such as reflective surfaces, failed image alignment, and inconsistent lighting were mitigated by creating a matte-black light box to ensure adequate contrast between the sample and background. Furthermore, the use of the Ortery TM turntable and an aperture of f/11 ensured consistent image placement and an image with a high Depth of Field. This research demonstrated that reliable and replicable results can be produced through hand-sample photogrammetry in a non-ideal context when imaging parameters and workflow settings are deliberately managed based upon real-time variables. These findings further constrain the best practices necessary for hand-sample photogrammetry in non-ideal environments. Moreover, the resulting models can be hosted online and downloaded as study tools at the discretion of any interested viewer, enhancing accessibility and supporting inclusivity in the geosciences.

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