Using Global Navigation Satellite System–Acoustic (GNSS-A) technique, we have been developing observation system on a moored buoy for continuous monitoring of seafloor crustal deformation. The sound speed structure near a warm current has heterogeneity, which is the main cause of a seafloor positioning error. Assuming a sloping structure, previous studies proposed sound speed model to reduce positioning error. We examined the validity of the model by comparing the estimated structure with the actual structure measured at multiple points around our observation site. The result shows that the gradient parameter estimated from GNSS-A data acquired by vessel is appropriate. The numerical examination indicates that modeling error caused by the misinterpretation of the depth of gradient layer occurs, and it can be suppressed by performing acoustic ranging at the point near the centroid of units. From the calculation of estimation error of sound speed variation, the predicted acoustic ranging error observed using the moored buoy staying near the centroid is 9.0 cm or below. Therefore, seafloor displacement can be detected with centimeter class via moored buoy in the basin of a warm current.

中文翻译：

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从GNSS-A测量结果估算海洋声速的时空变化，以使用系泊浮标进行观测

我们使用全球导航卫星系统声学（GNSS-A）技术，在系泊浮标上开发了观测系统，用于连续监测海底地壳变形。靠近暖流的声速结构具有异质性，这是海底定位误差的主要原因。假设结构是倾斜的，以前的研究提出了声速模型以减少定位误差。我们通过比较估计结构与在观察点周围多个点测得的实际结构，检验了模型的有效性。结果表明，从船舶获得的GNSS-A数据估计的梯度参数是合适的。数值检查表明，由于对梯度层深度的误解而导致了建模误差，并且可以通过在单位质心附近的点进行声音测距来抑制这种情况。根据声速变化的估计误差的计算，使用停留在质心附近的系泊浮标观察到的预测声测距误差为9.0cm以下。因此，可以通过热流盆地中的系泊浮标以厘米级检测海底位移。