Underwater acoustic positioning in multipath environment using time-of-flight signal group and database matching

Abstract

One of the challenges in underwater acoustic positioning is the occurrence of missing measurements and large errors in multipath environments, such as shallow water and harbor areas. In this paper, we propose a new underwater positioning method for multipath environments by using direct wave arrival time groups and database matching. The proposed method accurately measures baseline length from the impulse response of the underwater channel by calculating time window groups that cover the propagation time from the sound source to each hydrophone in advance and then extracting only the impulse response around the propagation time of the direct waves when the sound source exists in a certain region of the measurement space. The performance of the proposed method was experimentally evaluated in a static environment. The results showed that the proposed method achieved an accuracy of 0.03 m and a precision of 0.02 m in a test tank.

Detection of fish passing through a narrow path using reflected and transmitted ultrasonic waves

“…Low frequency ultrasound is generally used in ocean acoustics, to cope with the attenuation that occurs in the water. [14][15][16][17][18] The focus has generally been on the echoes obtained from the swim bladders of fish, because 90% of the echoes from fish when using low frequency ultrasound come from the swim bladder. 19) Megahertz-band ultrasound has been used for high-resolution measurements in other areas of research, such as nondestructive evaluation [20][21][22] and biomedical ultrasound applications.…”

Enhancing azimuth estimation in low-resolution underwater acoustic lens systems for advanced communication and positioning

“…We adopt M-sequence signals modulated with binary phase shift keying (BPSK), which are often used as signals with high autocorrelation. 34) The ToF is determined by peak detection of the cross-correlation function obtained between the transmitted signal from the communication partner and its own received signal.…”

Detection of free-swimming fish passing through a narrow passage using MHz-band ultrasonic reflected and transmitted waves

“…Low-frequency ultrasound with long wavelengths is usually used in underwater measurement and communication to propagate ultrasound over long distances with little attenuation. [7][8][9][10][11][12] HF ultrasound, such as MHz-band ultrasound with short wavelengths, has been used for a variety of purposes, including medical applications [13][14][15][16][17][18] and nondestructive testing. [19][20][21][22] Some studies in the field of hydroacoustics have used HF ultrasound, which can be used to measure shorter distances compared with low-frequency ultrasound.…”