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BLAST: Bringing land and sea together

HR Wallingford's SeaZone team has developed harmonised map layers as part of the BLAST project. With the purpose of Bringing Land and Sea Together, the BLAST project addressed coastal management and maritime safety in the North Sea region.

A European initiative

The four year BLAST project brought together 17 governmental organisations, universities and private companies from seven North Sea countries collaborated to harmonise and integrate spatial data across the land-sea boundary. Funded by the European Union’s Interreg IVB North Sea Region Programme, the project produced several state of the art results that will contribute to more harmonised and collaborative planning and management around the North Sea.

Linking the land and sea

The quality of data covering coastal regions can be limited for a number of reasons: land- and sea- surveys don’t always match up at the coastal margin, techniques for surveying low-water areas are limited, and the highly dynamic coastal environment can change more rapidly than maps and charts can be updated. In order to integrate geodata across the land-sea boundary and across national boundaries, BLAST addressed several existing issues. The first was a challenge related to vertical datums.

Evening out the surface of the sea

Each country in the North Sea region has its own model of how the earth, including the seabed under the North Sea, is shaped. As a result, each country’s model of its own territorial waters in the North Sea is distinctive. If these models in their respective vertical datums were joined up, there would be a “wall of water” where their at-sea boundaries meet. To remedy this issue, BLAST created a shared North Sea vertical reference frame and a transformation tool that permits users to convert data from one vertical datum to another. This now means that more intensive investigations of North Sea phenomena can be conducted, including modelling of sea level rise across the region.

Identifying the coast

Harmonised planning along the coast, in the intertidal margin and in shallow-water areas often requires a comprehensive view of the coastline. Since tides make the coastline a dynamic feature, the coast can be mapped in numerous ways, depending on the situation. For example, electronic navigational charts typically identify the coast based on the lowest astronomical tide (LAT); this is done to ensure the safety of navigation. On the other hand, land maps generally utilise local tidal observations such as Mean Sea Level (MSL).

To address this issue, BLAST extracted the best-scale coastlines from land maps and from electronic navigational charts, and combined them in a single map; the result demonstrates significant differences between the two coastlines. The new linked terrestrial-marine map, including its differentiation of the land- and sea coastlines, underlines the fact that existing maps and charts are developed for their respective purposes, and not necessarily for work across the coastal margin. It also underlines a need for a more streamlined foundation for planning cross-coastal development and conservation.

 More information on the project is available on the BLAST project website

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