Relocation of a seafloor transponder—Sustaining the GPS-Acoustic technique

Gagnon, K. L.; Chadwell, C. D.

doi:10.1186/bf03352692

Cited by 18 publications

(9 citation statements)

References 15 publications

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“…This was repeated from several locations around the transponder cluster to determine the position offset between the inactive and replacement unit. This offset was then rotated into the ECEF giving the location of the new transponder relative to the old transponder in the global frame (see Gagnon and Chadwell [2007] for details).…”

Section: Data and Resultsmentioning

confidence: 99%

Plate motion at the ridge‐transform boundary of the south Cleft segment of the Juan de Fuca Ridge from GPS‐Acoustic data

Chadwell

Spiess

2008

J. Geophys. Res.

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We measure the present‐day plate velocity of the Juan de Fuca Ridge 25 km off‐axis to be 63.6 ± 3.6 mm/a at S67.2°E ± 7.9° degrees (1‐σ) relative to the Pacific plate (PA). This velocity was derived from GPS‐Acoustic (GPSA) measurements in 2000, 2001, 2002, and 2003 that observed the position of a seafloor array (44°43′N,130°03′W, 2900 m depth) with a repeatability of ±4–6 mm. Three transient events at the Juan de Fuca Ridge and Blanco Transform account for ∼10% of this motion in viscoelastic modeling, suggesting that the observed GPSA‐PA velocity is due primarily to steady state plate dynamics. Subtracting the modeled transient motion gives a velocity of 57.3 ± 3.9 mm/a at S72.9°E ± 12.1° degrees (1‐σ), which is consistent at the 95% confidence level with the velocity calculated from the Wilson (1993) 0–0.78 Ma Euler pole. Therefore this site is interpreted to be in a region of continuous, full‐rate plate motion, a robust result of this study which holds with and without correcting for transient motions. These results provide direct geodetic evidence that spreading occurs predominantly within 25 km of the axis at this intermediate spreading‐rate ridge. Previously reported geodetic monitoring across the 1‐km‐wide axial valley from 1994–1999 and 2000–2003 shows no significant extension (Chadwell et al., 1999; Hildebrand et al., 1999; Chadwick and Stapp, 2002; W. W. Chadwick, personal communication, 2006) and seismic monitoring shows no activity. This suggests the crust between 0.5 and 25 km off‐axis accommodates ∼26 mm of aseismic deformation each year through some combination of near‐axis fault motion and elastic strain accumulation.

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Section: Data and Resultsmentioning

confidence: 99%

Plate motion at the ridge‐transform boundary of the south Cleft segment of the Juan de Fuca Ridge from GPS‐Acoustic data

Chadwell

Spiess

2008

J. Geophys. Res.

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“…In the first direction, circle moving, which means the survey vessel drives a circle centered on an underwater transponder, is recognized as the survey pattern of the highest positioning accuracy (Gagnon & Chadwell, 2007; Zhao et al., 2016). The latter two directions are related to distance intersection.…”

Section: Introductionmentioning

confidence: 99%

“…In the intersection, even though the transducer position is precise, ranging error, the error of the slant distance, cannot be ignored and it is, in fact, the most important factor that determines the positioning accuracy (Chen & Wang, 2011; Turetta et al., 2014; Yamada et al., 2002). In sailing‐circle positioning, although the plane accuracy has been improved a lot due to the geometric symmetry in x and y direction (see Gagnon & Chadwell, 2007), vertical accuracy is still poor, influenced by ranging errors (Ikuta et al., 2008).…”

Section: Introductionmentioning

confidence: 99%

Positioning Accuracy Model of Sailing‐Circle GPS‐Acoustic Method

Chen

Zhang

Zhao

et al. 2021

Earth and Space Science

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Precise positioning of underwater transponders plays a significant role on seafloor geodetic deformation research, ocean engineering and underwater navigation (e.g., Guo et al., 2009;Sato et al., 2013). The prevalent approach to achieve the underwater positioning is GPS-acoustic method (Fujita et al., 2006;Zhao, Chen, Wu, & Feng, 2018), which combines the kinematic global positioning system (GPS) on a survey vessel with acoustic commutative interrogation between the onboard transducer and the underwater transponder. Generally, the method can be divided into two parts: One is the vessel region and the other is the underwater region.

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“…In the last few decades, a number of instruments suited for marine deployments have been developed and used for continuous measurements of seafloor deformation including pressure gauges, tiltmeters, and acoustic transponders (Burgmann & Chadwell, 2014). In some cases, such as the GPS-Acoustic method and calibrated pressure sensors, it can be cost-and time-efficient to replace and relocate sensors or perform campaign-style surveys to capture long-term time series (Chadwell & Spiess, 2008;Fujita et al, 2006;Gagnon & Chadwell, 2007). These methods require benchmarks installed on the seafloor for accurate re-positioning.…”

Section: Introductionmentioning

confidence: 99%

Validation of Geodetic Seafloor Benchmark Stability Using Structure‐From‐Motion and Seafloor Pressure Data

Cook

DeSanto

2019

Earth and Space Science

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One commonly used method to measure and detect centimeter‐scale changes on land is structure‐from‐motion (SfM) photogrammetry, wherein sets of digital images are used to generate three‐dimensional spatial models. Subcentimeter accuracy useful for geodetic studies is achievable when these surveys are conducted on land or from the air. This method has made its way into marine environments by way of scuba, remotely operated vehicle, and autonomous underwater vehicle‐based surveys largely in the context of mapping. Repeated SfM photogrammetry surveys could be used to monitor changes in the stability of seafloor benchmarks and key sites as the interest in and need for marine geodetic measurements continues to grow. These studies require centimeter‐level accuracy or better, and some rely on accurate placement, positioning, or relocation of geodetic monuments, benchmarks, and instruments. We assessed the accuracy of the photogrammetric method for this purpose by simultaneously conducting a remotely operated vehicle‐based SfM photo survey to produce three‐dimensional spatial data, and a precise pressure survey to accurately measure height information. We found that the SfM survey agreed with the pressure survey height within its uncertainty of ±6.0 cm while using a standard, off‐the‐shelf camera adapted for underwater use. This level of relative accuracy would allow us to detect changes in geodetic benchmarks or instrumented sites between repeated surveys where large changes or the accumulation of small changes is expected within the scene over several years. We believe that centimeter‐level accuracy is obtainable with adjustments to the photogrammetry survey parameters, a higher‐resolution camera, and inclusion of additional coded targets.

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Relocation of a seafloor transponder—Sustaining the GPS-Acoustic technique

Cited by 18 publications

References 15 publications

Plate motion at the ridge‐transform boundary of the south Cleft segment of the Juan de Fuca Ridge from GPS‐Acoustic data

Plate motion at the ridge‐transform boundary of the south Cleft segment of the Juan de Fuca Ridge from GPS‐Acoustic data

Positioning Accuracy Model of Sailing‐Circle GPS‐Acoustic Method

Validation of Geodetic Seafloor Benchmark Stability Using Structure‐From‐Motion and Seafloor Pressure Data

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