The BalMarGrav project, co-financed under the Interreg Baltic Sea Region 2021-2027 program, aimed to improve the insufficient mapping of the marine gravity field in the southern and eastern Baltic Sea region. This task is very important due to the decision of the Baltic Sea Hydrographic Commission to implement a common height reference system (Baltic Sea Chart Datum 2000) for the Baltic Sea Region which is consistent to the European height system. This means that bathymetric measurements, nautical charts etc., which are needed for safe navigation, offshore infrastructure and sea traffic management, will be based on a so-called geoid model, just determined by measurements of the acceleration due to the gravity field of the Earth.

New marine gravity measurements to modern standards are very costly and time-consuming. The BalMarGrav project involved organisations from 8 countries of the Baltic Sea region (11 partner institutions, 6 associated organisations) to jointly rework gravity measurements made between the 1950s and 90s in the southern and eastern parts of the Baltic Sea. These campaigns were mainly carried out with the support of the Soviet Union's research infrastructure. During the period of independence from the Soviet Union and the political transition, much of this data was forgotten or underutilised.

The BalMarGrav project has built a transnational network of experts in the region to save and reprocess the fragmented historical gravity data and provide harmonized and validated open data product to the target groups: national sectoral agencies responsible for geodetic reference systems and national gravimetric databases, international governmental organisation (e.g. Baltic Sea Hydrographic Commission), nongovernmental organization (e.g. Nordic Geodetic Commission), as well as marine geophysical exploration companies and scientific community.

During the BalMarGrav project, 15 historical marine gravity datasets were secured from archives, reprocessed and validated by 16 modern marine gravity datasets. As a result, a single homogenized historical dataset for the southern and eastern Baltic Sea was developed and is available to the public from the Nordic Geodetic Commission gravity database. The download of the developed dataset was tested by 11 institutions, including 7 institutions that were not Project Partners or Associated Organisations. The dataset has been also incorporated into national databases. The good quality of the revitalized data, comparable to that of modern marine gravity measurements, was confirmed by comparisons with regional and global gravity models from different sources and techniques. In addition, 3 reports on historical (here), modern (here) and homogenized marine gravity datasets (here), as well as maps of the so-called free-air gravity anomaly and the Bouguer anomaly have been developed and posted for free download at the project web-page (here).