Frontiers in Earth Science ( IF 2.689 ) Pub Date : 2021-01-14 , DOI: 10.3389/feart.2021.600993 Yuto Nakamura; Yusuke Yokota; Tadashi Ishikawa; Shun-ichi Watanabe
The Global Navigation Satellite System-Acoustic ranging combination technique (GNSS-A) has enabled us to measure seafloor crustal deformation in the precision of centimeters, leading to numerous discoveries of subseafloor tectonic phenomena. The moving observation conducted by our research group allows us to measure both the horizontal and vertical absolute positions of a reference point on the seafloor. However, the observation frequency of our GNSS-A observation system is still insufficient to observe short-term phenomena. This paper focused on the possibility to reduce the observation time per a seafloor site by shrinking the seafloor transponder array size and the survey line radius, which were empirically defined to be equal to the seafloor site depth in the early research. We evaluated the effects of changing these sizes on the GNSS-A positioning accuracy by conducting a series of numerical experiments. The results of the numerical experiments indicated that for a seafloor site with a depth of 3,000 m, the positioning accuracy is rapidly degraded as the transponder array size and the survey line radius are reduced to less than 3,000 m. Additional experiments done for transponder array sizes and survey line radii around 2,000–4,000 m revealed that shrinking the survey line radius has a dominant effect on the decrease in positioning accuracy. Thus, shrinking the transponder array size and the survey line radius is not a suitable option for reducing observation time, and the empirically defined observation configurations are concluded to be quite optimal when regarding both the positioning accuracy and the observation time.
全球导航卫星系统-声音测距组合技术（GNSS-A）使我们能够以厘米的精度测量海底地壳变形，从而导致了许多海底构造现象的发现。我们的研究小组进行的移动观测使我们能够测量海底参考点的水平和垂直绝对位置。但是，我们的GNSS-A观测系统的观测频率仍然不足以观测短期现象。本文着眼于通过缩小海底应答器阵列的大小和测量线半径来减少每个海底站点的观测时间的可能性，在经验上，这被定义为等于海底站点的深度。通过进行一系列数值实验，我们评估了改变这些尺寸对GNSS-A定位精度的影响。数值实验结果表明，对于深度为3,000 m的海底站点，随着应答器阵列尺寸和测量线半径减小到小于3,000 m，定位精度会迅速下降。对应答器阵列大小和2,000-4,000 m左右的测量线半径进行的其他实验表明，缩小测量线半径对降低定位精度具有主要影响。因此，缩小应答器阵列的大小和测量线半径不是减少观察时间的合适选择，
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