Project updates, including ongoing and past at-sea and community activities associated with the Near-Trench Geodetic Experiment
Planned and operational GNSS-Acoustic sites in Cascadia: previously deployed sites (white triangles), community experiment sites established and surveyed in 2022 (orange triangles) and sites planned for completion and surveying in 2023 (red circles)
In July, UC San Diego, Univ. Washington, and Univ. Kansas participated in a research expedition on the R/V Thomas Thompson to begin deploying instrumentation for the community experiment. Over the course of 9-days they deployed 11 of the GNSS-Acoustic transponders from the community instrument pool, establishing 3 of the six sites proposed off shore Oregon (orange triangles at left) and partially installing a 4th site (NSS1). They also deployed the JASON ROV to reoccupy concrete benchmarks at the existing site NNP1 using legacy equipment from previous GNSS-Acoustic experiments in the region.
In addition to the above, they deployed one of the instrument pool Wave Gliders to collect positions at all of these sites. The Wave Glider collected two data sets at each of the new sites: a set of acoustic ranges from a circular drive* around each of the individual transponders and a set of acoustic ranges from the center of each transponder array. The survey from the array center collected range data for transponder-triads simultaneously and allowed for initial array-center positioning with cm-level uncertainty, the first data points in the position time series for each of the new sites.
A follow-up expedition is currently planned for July 2023, during which we plan to install the remaining sites in the off shore Cascade region (NSS1, NQU1, and NLP1). At this time we will also deploy a Wave Glider to collect positions at each site in the array.
We are still awaiting shiptime for field activities of Alaska. This may not happen until 2024.
* The circular drives allow us to approximately triangulate the initial positions of each transponder with an uncertainty of 10-20 cm, which is good enough to correct for any distance the transponders may have drifted from their drop points as they sank through the water column