Geology topics

Gerry Hatcher

Publications and source records attributed to Gerry Hatcher.

3 recordsLinked to original sources

USGS2019

Integrating structure from motion, numerical modelling and field measurements to understand carbonate sediment transport in coral reef canopies

Reef canopies are complex and extremely variable across a range of spatial scales. This variability affects the velocity above as well as within the canopy, and directly impacts the transport of sediment along the bed as well as suspended in the water column. How a canopy affects the transport of sediment is important to understand and predict changes in the position of the adjacent shoreline, particularly as reefs change. In this study, high-resolution seabed complexity models derived from photogrammetry for low roughness and high roughness canopy sites at Moloka’i (Hawai’i) are combined with direct field measurements and three-dimensional numerical modelling to investigate these canopy and sub-canopy impacts on velocity and sediment transport.

Hawaii↗

USGS2016

End of the chain? Rugosity and fine-scale bathymetry from existing underwater digital imagery using structure-from-motion (SfM) technology

The rugosity or complexity of the seafloor has been shown to be an important ecological parameter for fish, algae, and corals. Historically, rugosity has been measured either using simple and subjective manual methods such as ‘chain-and-tape’ or complicated and expensive geophysical methods. Here, we demonstrate the application of structure-from-motion (SfM) photogrammetry to generate high-resolution, three-dimensional bathymetric models of a fringing reef from existing underwater video collected to characterize the seafloor. SfM techniques are capable of achieving spatial resolution that can be orders of magnitude greater than large-scale lidar and sonar mapping of coral reef ecosystems. The resulting data provide finer-scale measurements of bathymetry and rugosity that are more applicable to ecological studies of coral reefs than provided by the more expensive and time-consuming geophysical methods. Utilizing SfM techniques for characterizing the benthic habitat proved to be more effective and quantitatively powerful than conventional methods and thus might portend the end of the ‘chain-and-tape’ method for measuring benthic complexity.

Coral Reefs↗

USGS2016

The development of small, cabled, real-time video based observation systems for near shore coastal marine science including three examples and lessons learned

The effects of climate change on the near shore coastal environment including ocean acidification, accelerated erosion, destruction of coral reefs, and damage to marine habitat have highlighted the need for improved equipment to study, monitor, and evaluate these changes [1]. This is especially true where areas of study are remote, large, or beyond depths easily accessible to divers. To this end, we have developed three examples of low cost and easily deployable real-time ocean observation platforms. We followed a scalable design approach adding complexity and capability as familiarity and experience were gained with system components saving both time and money by reducing design mistakes. The purpose of this paper is to provide information for the researcher, technician, or engineer who finds themselves in need of creating or acquiring similar platforms.

Conference Paper↗