Quantitative identification of causes of instrumental acoustic signal distortion in Global Navigation Satellite System–Acoustics Combination observations.

This article focuses on investigating the causes and characteristics of acoustic signal distortion in the Seafloor Geodetic Observation–Array (SGO-A), operated by the Japan Coast Guard, which uses the Global Navigation Satellite System–Acoustics combination (GNSS-A) technique for precise seafloor crustal deformation measurements. Through underwater acoustic communication experiments and waveform analysis, the study identifies that signal degradation arises primarily from internal electrical circuits—specifically transistor and driver integrated circuit distortions during high-voltage signal amplification—and from sonar equipment effects at both surface and seafloor stations. The findings highlight that conventional signal identification methods based on simple correlation may introduce significant errors, suggesting the need for timing-based waveform identification and continuous monitoring of transmitted and received signals to improve GNSS-A positioning accuracy.