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Abstract:
The global navigation satellite systems (GNSS) have achieved near-real-time precise positioning and real-time or near-real-time applications based on the static delay corrections and real-time zenith delay estimation. However, precise GNSS-acoustic (GNSS-A) positioning currently depends on in-field sound speed measurement causing a huge cost and preventing real-time GNSS-A applications. This contribution is to develop acoustic delay correction models for seafloor geodetic positioning by using the ocean environment observations including the ocean temperature, sanity and depth, instead of using in-field sound speed measurements. For applying the global long-term mean ocean temperature and sanity product to GNSS-A observation corrections, a static acoustic delay correction approach is proposed in the context of absence of the in-field SSP; then, zenith delay products for performing the static acoustic delay correction are established; GNSS-A positioning model appended with the static delay corrections and real-time acoustic delay estimation is proposed. The proposed models are verified by the long-term seafloor geodetic array observations. It shows that, the proposed approach can achieve almost the same result with that of based on the in-field SSP. The influence of substituting the in-field SSP with the static delay correction on the horizonal positioning is just serval mm, while influence on the vertical positioning is only 2-4 cm in the standard deviation sense. This kind of influence on the tectonic movement can be further reduced when analyzing 10-years long-term seafloor geodetic coordinate time series.
