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Volume 31 Issue 9 (September 2021)

GSA Today

Article, pp. 4-9 | Full Text | PDF

Virtual Outcrops in a Pocket: The Smartphone as a Fully Equipped Photogrammetric Data Acquisition Tool

Amerigo Corradetti*

Dept. of Mathematics and Geosciences, University of Trieste, Trieste, Italy

Thomas D. Seers

Dept. of Petroleum Engineering, Texas A&M University at Qatar, Doha, Qatar

Andrea Billi

Consiglio Nazionale delle Ricerche, IGAG, Rome, Italy

Stefano Tavani

Consiglio Nazionale delle Ricerche, IGAG, Rome, Italy, and DiSTAR, Università di Napoli Federico II, Napoli, Italy

Abstract

Since the advent of affordable consumer-grade cameras over a century ago, photographic images have been the standard medium for capturing and visualizing outcrop-scale geological features. Despite the ubiquity of raster image data capture in routine fieldwork, the development of close-range 3D remote-sensing techniques has led to a paradigm shift in the representation and analysis of rock exposures from two- to three-dimensional forms. The use of geological 3D surface reconstructions in routine fieldwork has, however, been limited by the portability, associated learning curve, and/or expense of tools required for data capture, visualization, and analysis. Smartphones are rapidly becoming a viable alternative to conventional 3D close-range remote-sensing data capture and visualization platforms, providing a catalyst for the general uptake of 3D outcrop technologies by the geological community, which were up until relatively recently the purview of a relatively small number of geospatial specialists. Indeed, the continuous improvement of smartphone cameras, coupled with their integration with global navigation satellite system (GNSS) and inertial sensors provides 3D reconstructions with comparable accuracy to survey-grade systems. These developments have already led many field geologists to replace reflex cameras, as well as dedicated handheld GNSS receivers and compass clinometers, with smartphones, which offer the equivalent functionality within a single compact platform. Here we demonstrate that through the use of a smartphone and a portable gimbal stabilizer, we can readily generate and register high-quality 3D scans of outcropping geological structures, with the workflow exemplified using a mirror of a seismically active fault. The scan is conducted with minimal effort over the course of a few minutes with limited equipment, thus being representative of a routine situation for a field geologist.

Manuscript received 5 Mar. 2021. Revised manuscript received 19 May 2021. Manuscript accepted 25 May 2021. Posted 1 July 2021.

© The Geological Society of America, 2021. CC-BY-NC.

https://doi.org/10.1130/GSATG506A.1

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