Reliably and accurately charted shipping lanes are key to ensuring safety at sea. The FAMOS project aims to increase and improve the safety, efficiency and cost-effectiveness of the shipping industry. With more accurate information on depths, shipping routes can be optimised according to the ship’s draft and fuel consumption.
The hydrographic surveying conducted in the FAMOS project enables the project’s researchers to unify the vertical datums of the height systems used in nautical charts of the Baltic Sea region. The value of the vertical datums differs between charts created in different countries, and at its greatest, the difference is as much as 25 centimetres.
“FAMOS consortium aims for a unified height system for around the Baltic Sea. It is crucial for Lantmäteriet to support the project, which means that we get the same height system both on land and sea. This is also the same system that will be used by almost all countries around the Baltic Sea, which is really excellent,” says project manager Jonas Ågren from Lantmäteriet.
“Unified height system allow better agreement and consistency amongst stakeholders and policymakers for the establishment of across-border economical infrastructure, such as underwater pipelines, power cables and offshore wind turbines,” says Artu Ellmann, professor of geodesy in the Tallinn University of Technology.
Unity increases accuracy – accuracy increases safety
To unify the nautical charts, a more accurate geoid model must be created for the Baltic Sea region. The geoid is a model of the Earth that describes the shape the oceans would take at rest. This makes it a very relevant model when measuring the depth of the ocean. The geoid model can be improved with gravity measurements. Even on Earth, gravity is inconsistent: its force varies depending on location, and it is under constant change. Gravitational pull is affected by post-glacial rebound, for example.
Gravitational measurements have traditionally been taken as single measurements on islands, islets, the seafloor and sea ice, which leaves vast areas completely uncharted. These areas have now been charted with the gravitational measurements taken in the FAMOS project with next generation instruments.
“When we combine all the marine gravimetry campaigns organised within the FAMOS project and calculate the new geoid model for the Baltic Sea region, we will achieve an accuracy of 5 centimetres for the geoid heights, which is the target accuracy for the project. The more accurate model will enable safer navigation, especially in ports and coastal waters,” says researcher Timo Saari from the Finnish Geospatial Research Institute.
The most recent measurements were taken in the Eastern Gulf of Finland
Twenty marine gravimetry campaigns were conducted in the FAMOS project around the Baltic Sea. The project comprises 15 organisations from seven countries. The Finnish Geospatial Research Institute was involved in the gravimetry campaigns of 2015, 2017 and 2018.
The 2018 campaign was conducted as a joint effort between the Finnish Geospatial Research Institute, the Geological Survey of Finland (GTK) and the Swedish mapping, cadastral and land registration authority Lantmäteriet. The aim of the campaign was to take gravitational and satellite measurements for Finnish sea areas in the Eastern Gulf of Finland, where GTK’s research vessel Geomari was sailing. The continuous measurements taken on board Geomari completed the gravity data on Finland.
Making data from different countries comparable
Height data obtained with measurements taken in sea areas is usually given in reference to a national height system. These height systems often use the mean sea level as the vertical datum, which is often determined to be at a different height in different height systems.
“The variation in the chart datums is often the cause of errors in research, especially if knowing the exact depth of water is crucial. Harmonising the vertical datums will significantly improve the comparability of datasets from different countries, and it will even allow us to combine them. It also increases the reliability of research results,” says geologist Kimmo Alvi from GTK.
Researcher Timo Saari, The National Land Survey, +358 50 357 4315, firstname.lastname@example.org
Geologists Kimmo Alvi, Geological Survey of Finland, +35840 8250 510, email@example.com
In Finland, Traficom has started to gradually introduce the new vertical reference system in its nautical activities.
The FAMOS project is partly funded by the EU.