New imaging techniques enhance studies of underwater habitats in the Baltic
Revolutionary new imaging techniques that will radically speed up the ongoing surveys of underwater environments in the Baltic Sea have been developed through a project led by Metsähallitus. Applied more widely, these ground-breaking new methods could greatly facilitate decision-making on issues including marine planning, dredging, projected bridges and wind power facilities, sand and gravel extraction, and marine protected areas.
The ULTRA Project, led by Metsähallitus Natural Heritage Services, was set up to examine whether aerial surveys using LiDAR (Light Detection and Ranging) laser sensing techniques could be used to survey submarine habitats and ecosystems, as well as sea depths. There is an urgent need to conduct surveys of marine ecosystems, due to the many pressures on marine areas. LiDAR sensing methods have already been used in other parts of the world to measure sea depths, and in Finland mainly to survey terrestrial topography.
Surveys were conducted from aircraft for the project in September 2009 in both Finnish and Swedish marine waters. The results were positively surprising, particularly in Finnish waters. The LiDAR techniques produced much more detailed data on depths in shallow waters than anticipated. It also proved possible to use data from the laser surveys to analyse vegetation on the sea floor – the first time this has been done anywhere. The reliability of the survey results surprised marine scientists. Accuracy rates of around 80-90% were revealed after conventional surveys were conducted to confirm data. The maps produced during the reliability trials themselves have proven to be accurate enough to use as such in future marine planning work.
The greatest advantage of LiDAR techniques is their speed. Using conventional survey methods a team of marine scientists is able to survey marine areas of about 10 km2 each summer surveying season. The new aerial laser surveying methods can now be used to survey about 30 km2 every day.
Discovering the mysteries of the Baltic
Very little is yet known about the distributions and statuses of marine species and habitats in the Baltic Sea. Current surveying methods and resources do not enable scientists to obtain sufficient basic data rapidly enough to contribute to decision-making on the use and conservation of marine areas or vital environmental impact assessments for projected developments.
Shallow marine waters are particularly problematic in this context. Conventional echosounding survey methods do not produce reliable information on the species and habitats found in shallow waters, which often have many valuable natural features, but also tend to be the marine areas under most pressure.
“Significant projects utilizing marine resources are continually being developed. From Finland’s perspective it would be important for us to be able to rapidly and reliably indicate where such schemes would be suitable,” says ULTRA’s project manager Michael Haldin, of Metsähallitus Natural Heritage Services. “But so far underwater environments have only been surveyed in well under one percent of Finland’s marine areas. This problem has been highlighted in contexts including the parliamentary environment committee’s statement on the government’s Baltic Sea Report. The effectiveness and outcomes of underwater surveys are totally dependent on the methods and resources used.”
Although the first research findings obtained using the LiDAR method have been excellent, techniques still need to be developed considerably before they can be used more extensively.
“The method has to be standardised, which will require more collaboration between Metsähallitus, the regional authorities from Västerbotten County and researchers from the Swedish armed forces. Preparations for the new ULTRA 2 project will now be initiated this summer,” says Haldin.
The Hawkeye II LiDAR equipment tested in the ULTRA Project is so far only used in two aircraft anywhere in the world. It was originally designed to detect submarines and mines, but is now commercially available as a tool for marine bathymetric surveys. The results of the ULTRA Project should lead to its much wider application in surveying ecological features.
“Though we must continue developing the method, the results we have obtained so far have been extremely significant. There is a great need for the wider application of this technique, to ensure that marine areas and resources are utilised without any further damage to the sensitive natural environments of the Baltic Sea,” says Haldin.
For more information:
Michael Haldin, senior adviser, Metsähallitus Natural Heritage Services: Tel. +358 40 5058 580 (text messages can also be sent to request contact)
Päivi Rosqvist, communications manager, Metsähallitus Natural Heritage Services: Tel: +358 400 425 666
LiDAR aerial surveying techniques in brief
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LiDAR (Light Detection and Ranging) laser surveying techniques are used to survey the seabed from an airplane or helicopter.
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The LiDAR method is based on the ways laser rays are reflected from the seabed. The research premise has been that in addition to revealing water depths, reflected signals should also contain useful information about the nature of the seabed and its vegetation, since these factors also affect the characteristics of reflected laser signals.
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The method’s advantages include speed and accuracy. Data can be compiled for an area of 30 km2 in a single day for survey points spaced at two-metre intervals. The disadvantage is that the method can be only used for shallow waters with depths of less than about 10 metres.
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The new method was tested in two areas: the Rönnskär archipelago in Finland and Sävarfjärden in Sweden. Sävarfjärden is situated about 100 km north of Rönnskär in the Bothnian Bay. which has low salinity, while Rönnskär is in the Bothnian Sea south of the Kvarken archipelago, where salinity levels are higher. Salinity levels are a major factor shaping the species mix in Baltic marine ecosystems. For purposes of comparison other survey methods were also tested in the same waters. Data on seabed conditions was collected in Sävarfjärden using a video camera, while the sea bed was surveyed in Rönnskär by divers using submarine scooters. Results were analysed by comparing the data obtained from the LiDAR signals with the findings of the conventional surveys. This analysis was conducted at the Swedish Defence Research Agency (FOI).
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The ULTRA Project also evaluated the significance of the findings and potential applications of LiDAR surveys for the authorities working with marine administration and resources.
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Metsähallitus’s main partner in the ULTRA Project has been the county administration of Västerbotten in Sweden. Other partners have included: Meritaito Oy; the Regional Council of Ostrobothnia; the Swedish Defence Research Agency (FOI); The City of Umeå; The Finnish Game and Fisheries Research Institute; The South Ostrobothnia Centre for Economic Development, Transport and the Environment; the Geological Survey of Finland; and AquaBiota Water Research in Sweden. Owing to its social and regional significance, the project also obtained funding from the Botnia-Atlantica region’s Interreg IVA Programme, the Regional Council of Ostrobothnia, and the county administration of Västerbotten.