News
The Old Surveyor
I don’t feel like an old surveyor but I have gained some experience as a hydrographic surveyor as I have been involved in surveying since 1984. In my early days hydrographic surveys were generally carried out using a ‘range range’ positioning system and a single-beam echo sounder without any other sophisticated equipment connected. Since then a lot of water has passed through the waterways which The Royal Danish Administration of Navigation and Hydrography (RDANH) has responsibility for.
Onboard SKA-11 RDANH carried out a test survey in a southern fjord in Greenland last year. The test survey was carried out in order to verify or disprove that hydrographic surveys carried out with a multibeam system are a profitable solution. In order to carry out the test survey RDANH rented a SeaBat 8111 100 kHz multibeam echo sounder from Reson. The SeaBat 8111 system used for the survey covered a swath width of 150 deg. For data collection the NaviBat software package and for processing data NaviEdit from EIVA was used. Processing the data in-house software ‘Vise’ and ‘Semi’ was used. These software packages are freeware and can be obtained by contacting eeg@fomfrv.dk. The GeoZui software which can be obtained from http://www.ccom-jhc.unh.edu/vislab/GeoZui.html has been used for presentation and explanation. The GeoZui is also freeware.
In general, only bathymetric data covering 120 deg swath width has been used. But surveying along the steep slopes close to the shore in the fjord the complete swath width has been used.
The SeaBat 8111 multibeam was used in the Tasermiut Fjord at a water depth between 6 and 350 metres for six days to carry out the survey. In order to cover the same area using single-beam techniques the survey would have lasted no less than 15 days using two SKA-boats. Even using two SKA-boats 100 per cent coverage would not have been achieved. Using the multibeam technique RDANH has now proven that the survey time to cover larger areas in the Greenland waterways can be reduced. In other words, the survey time can be reduced drastically in this region of RDAHN’s responsibility.
The drawback is that even in the Greenland waterways with a general deep water depth of several hundreds metres, the multibeam cannot be used as a standalone system as there are areas which are shallow and complex. So there will still be a need for single-beam echo sounders.
RDANH is now planning to implement a multibeam system on one of the two SKA-boats used for surveying around Greenland.

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