A stochastic model for precise GNSS/acoustic underwater positioning based on transmission loss of signal intensity

Global navigation satellite system (GNSS)/acoustic (GNSS/A) underwater positioning technique is widely applied in the fields of marine scientific research and engineering applications. A more accurate and reliable stochastic model is required for precise GNSS/A underwater positioning. The transmission loss (TL) describes the decrease in acoustic intensity associated with a bubble curtain or other damping structure at a given frequency. It can characterize the noise level of acoustic ranging measurements in the presence of background noise in the ocean. This contribution proposes a stochastic model for precise GNSS/A underwater positioning based on the transmission loss of signal intensity. The transmission loss of signal intensity is obtained according to the acoustic ray-tracing method and then used in the proposed stochastic model to calculate the variance matrix of acoustic ranging measurements. To verify the performance of the proposed method, a lake experiment was carried out. The results show that the ray incidence angle stochastic model performs worse in seafloor transponder positioning if acoustic observations contain gross errors, especially when the observations with low incidence angles contain gross errors. The proposed method provides a stable positioning performance. The positioning accuracy with the proposed method is improved by approximately 30–83% over the equal-weighted stochastic model and 10–82% over the ray incidence angle stochastic model.