Cit:Thorn.etal:2021

Autor	Thorn, A.J.; Collie, B.T.
Jahr	2021
Titel	Micro-photogrammetry to monitor salt impact on petroglyphs
Bibtex	@inproceedings { Thorn.etal:2021, title = {Micro-photogrammetry to monitor salt impact on petroglyphs}, booktitle = {Proceedings of SWBSS 2021 – Fifth International Conference on Salt Weathering of Buildings and Stone Sculptures}, year = {2021}, editor = {Lubelli, B.; Kamat, A.A.; Quist, W.J.}, pages = {141-151}, publisher = {TU Delft Open}, note = {A project focusing on the potential industrial impact on a cluster of one million engraved boulders in a remote desert location, requires, among other metrics, the study of micro-spalling because of potential crypto-fluorescence, or surface depo-sition, both of which change the surface morphology at the micro-scale, including pre-spall swelling. Project outcomes include deploying technologies readily implemented in-field, ultimately by locally trained operators.This paper outlines the system, in cluding the operation of a portable fully automated triaxial scanning frame and the processing technologies deployed to produce a 3D photogrammetric model, and the further processing of that model to provide long-term indicators of change.All three axes are programmed to scan with a single button press, gathering up to 5,600 images over the target within 150 minutes. To acquire fully focused Z-axis images, a stack of 20 images is acquired at 1 mm vertical intervals. The other dimensions are set to image any given point 4-9 times, depending on the overlap. System screening identified a 36Mp DSLR fitted with a Zeiss 4x objective as the most effective imaging system, including being an existing piece of field equipment used for other studies, only requiring the addition of the objective and its mount.The Z- axis image stacks are processed through Helicon Focus to reduce the 5,600 images to 250 stacks, submitted to Agisoft Metashape for model construction. The model is interrogated using various measurement programs including CAD, Metashape and Cloud Compare to establish vital change metrics.}, key = {SWBSS 2021}, url = {https://predict.kikirpa.be/wp-content/uploads/2021/12/SWBSS2021_Procedings.pdf}, author = {Thorn, A.J. and Collie, B.T.} }
DOI
Link	Datei:SWBSS-2021 Thorn etal 141-151.pdf
Bemerkungen	in: Lubelli, B.; Kamat, A.A.; Quist, W.J. (Hrsg.): Proceedings of SWBSS 2021 – Fifth International Conference on Salt Weathering of Buildings and Stone Sculptures,TU Delft Open 141-151

Eintrag in der Bibliographie

[Thorn.etal:2021]

Thorn, A.J.; Collie, B.T. (2021): Micro-photogrammetry to monitor salt impact on petroglyphs. In: Lubelli, B.; Kamat, A.A.; Quist, W.J. (Hrsg.): Proceedings of SWBSS 2021 – Fifth International Conference on Salt Weathering of Buildings and Stone Sculptures,TU Delft Open 141-151, Webadresse.

Keywords

Micro-photogrammetry, delamination, crypto-fluorescence, micro-spalling

Abstract

A project focusing on the potential industrial impact on a cluster of one million engraved boulders in a remote desert location, requires, among other metrics, the study of micro-spalling because of potential crypto-fluorescence, or surface depo-sition, both of which change the surface morphology at the micro-scale, including pre-spall swelling. Project outcomes include deploying technologies readily implemented in-field, ultimately by locally trained operators.This paper outlines the system, in cluding the operation of a portable fully automated triaxial scanning frame and the processing technologies deployed to produce a 3D photogrammetric model, and the further processing of that model to provide long-term indicators of change.All three axes are programmed to scan with a single button press, gathering up to 5,600 images over the target within 150 minutes. To acquire fully focused Z-axis images, a stack of 20 images is acquired at 1 mm vertical intervals. The other dimensions are set to image any given point 4-9 times, depending on the overlap. System screening identified a 36Mp DSLR fitted with a Zeiss 4x objective as the most effective imaging system, including being an existing piece of field equipment used for other studies, only requiring the addition of the objective and its mount.The Z- axis image stacks are processed through Helicon Focus to reduce the 5,600 images to 250 stacks, submitted to Agisoft Metashape for model construction. The model is interrogated using various measurement programs including CAD, Metashape and Cloud Compare to establish vital change metrics.

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