Gravity Measurements along Commercial Ferry Lines in the Baltic Sea and Their Use for Geodetic Purposes

Abstract

In 2017 and 2018 GFZ performed two gravimetry campaigns on commercial ferries in the Baltic Sea.The nature of such "non-dedicated" campaigns is different from "dedicated" campaigns that are performed on research vessels with tracks planned according to gravity measurement needs. The nondedicated campaigns use non-survey vessels or survey vessels running for other purposes such as hydrographic measurements, which may require additional corrections. To assess the usefulness of non-dedicated campaigns, we analysed gravity measurements collected on two commercial ferries as part of the EU funded FAMOS project. Besides the typical marine gravimetry corrections, we also investigated the corrections for the vertical accelerations due to the ship's movement and the dynamical effect due to the cross-coupling between horizontal and vertical acceleration components.Taking the latter two corrections into account partly leads to slight improvements, but our results also demonstrate that the standard processing without the two corrections, as used in most of the dedicated campaigns, already delivers good quality end products that fulfil the requirements of a typical marine gravimetry survey with an uncertainty of about 1 mGal. Our findings suggest that gravimetry campaigns on commercial ferries can be used to complement dedicated marine gravimetry campaigns and contribute to geodetic purposes.

Treatment of Tide Gauge Time Series and Marine GNSS Measurements for Vertical Land Motion with Relevance to the Implementation of the Baltic Sea Chart Datum 2000

“…Offshore, BSCD2000 will be realized through GNSS and high-resolution (0.01 × 0.02 arc-deg) geoid modeling, while onshore, BSCD2000 will be compatible with the national height system realizations of the Baltic Sea countries (e.g., EH2000, N2000, and RH 2000) and will coincide with national geoid models to allow seamless height transitions (this will be achieved through the blending of the models, developed by different geoid computation centers [50]). For this purpose, the Baltic Sea is being densely covered by ship-and airborne marine gravity data [24,[51][52][53][54][55] to allow high-accuracy marine geoid modeling. Note that since the provided discussion is limited to the Estonian, Finnish, and Swedish height system realizations, an interested reader is encouraged to read additional details concerning BSCD2000 and the other Baltic Sea countries from [34,49,50].…”

Marine Gravimetry and Its Improvements to Seafloor Topography Estimation in the Southwestern Coastal Area of the Baltic Sea

“…With the updated gravimeter Chekan-AM, the drift in the campaign DENEB2017 was very stable with a normal value of 0.50 mGal/day, as shown in Figure 3c. Furthermore, the gravimetry measurements of the campaign URD2017 (also another campaign Finnlady2018) implemented on ferries also had a very stable drift [47,48].…”

“…After the gravimeter Chekan-AM was updated, the first campaign of DENEB2017 showed significant improvements: The absolute values of Min (−0.76 mGal) and Max (0.52 mGal) of gravity differences at crossover points were within 1.00 mGal, and the RMS value reached 0.30 mGal, which is close to the current claimed the highest precision of 0.10-0.20 mGal. In addition, the gravimetry measurements of the campaign URD2017 (also another campaign Finnlady2018) implemented on ferries were at the precision level of 1.00 mGal along the tracks [47,48].…”

The influence of the Earth’s magnetic field on strapdown inertial gravimetry using Q-Flex accelerometers: static and dynamic experiments

“…In most dynamic gravimetry campaigns, horizontally stabilised spring-type gravimeters have been installed, e.g. Nettleton et al (1960), Brozena et al (1997), Forsberg and Olesen (2010), Lu et al (2017) and Ince et al (2020). Since the 1990s, the use of inertial measurement units (IMUs) strapped-down to the moving vehicle became more and more convenient as it was shown that the accuracy is comparable to that of spring type gravimeters (Glennie et al 2000;Becker et al 2015;Johann et al 2020;Yuan et al 2020).…”