Doing Fieldwork on the Seafloor: Photogrammetric Techniques to Yield 3D Visual Models from ROV Video

Computers & Geosciences, published online 22 October 2012

Tom Kwasnitschka, Thor H. Hansteen, Colin W. Devey, and Steffen Kutterolf

“Highlights

• A new technology for deep-sea micro scale mapping is demonstrated.
• Photogrammetry based on ROV video yields 3D models.
• Quantitative data extraction yields geoscientific insights.
• The workflow is readily replicable and based on industrial software.

“Remotely Operated Vehicles (ROVs) have proven to be highly effective in recovering well localized samples and observations from the seafloor. In the course of ROV deployments, however, huge amounts of video and photographic data are gathered which present tremendous potential for data mining. We present a new workflow based on industrial software to derive fundamental field geology information such as quantitative stratigraphy and tectonic structures from ROV-based photo and video material.

Warping effects due to missing lens distortion parameters (a) superimposed on the correct reconstruction (b). Both models have been aligned at the first camera pose (c), where deviations in the model geometry and position are already apparent. The largest dislocation (gray arrow) in position and camera angle is found between the last images, (d) showing the warped path and (e) the correct path, deviating 29° in pitch, 8° in roll and 1.8° in heading. Crosses mark the location of a corresponding feature referenced in the text. Measurements of a corresponding bedding plane (white planes) indicate a strong deviation in strike (67°, lines) and dip (12°, arrows). The light transparent model (f) and camera planes (g) illustrate the model, which has been aligned to the track coordinates, resulting in positioning and also scaling errors. The white grid represents the true horizontal plane.

“We demonstrate proof of principle tests for this workflow on video data collected during dives with the ROV Kiel6000 on a new hot spot volcanic field that was recently identified southwest of the island of Santo Antão in the Cape Verdes. Our workflow allows us to derive three-dimensional models of outcrops facilitating quantitative measurements of joint orientation, bedding structure, grain size comparison and photo mosaicking within a georeferenced framework. The compiled data facilitate volcanological and tectonic interpretations from hand specimen to outcrop scales based on the quantified optical data. The demonstrated procedure is readily replicable and opens up possibilities for post-cruise “virtual fieldwork” on the seafloor.”

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