The survey data are pre-processed on board. Depending on the available processing capacity, the evaluation is carried out either on board or onshore. Processing of the data is geared to the intended resolution taking into account the morphology and importance of the particular area surveyed and the chart scales. The following products are derived from the surveys:
- Sounding data, i.e. quickly available digital depth information obtained by simplified evalutation
- Hydrographic survey data, i.e. quality-evaluated digital depth data and survey lines
- Topographic map of the sea floor which contains not only hydrographic survey data but additional information such als coastlines, aids to navigation, wrecks, fixed points, grid. Topographic maps are available digitally, in pdf format, or as plots.
The decision on the map format is made in the course of the evaluation. As the scope of tasks depends on local conditions, the maps produced are no longer necessarily rectangular and completely filled. Also the traditional 1cm spacing between two lines on the map, in the case of single-beam sounding, is not always used because, in order to achieve full survey coverage, the resolution during the survey may be higher than that used later in the evaluation.
Section from a topographic map of the sea floor
Depending on the importance of the objects found, they are either entered in the database of underwater obstructions or are stored separately if they do not pose an immediate risk.
The agreement on the first harmonised re-survey of the Baltic Sea is a large step toward improving the safety and efficiency of navigation in this vulnerable marginal sea with its high traffic density, where especially transports of dangerous cargo will continue to increase. A comparable scheme for the North Sea will be introduced in 2006.
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