The MRU and SRF Aligned (II and III)

The alignment of the motion reference unit (MRU) is important for the accuracy of a multi-beam survey. The patch test is mostly used to solve angular offsets between the multi-beam head and the MRU; however, this does not solve all the aspects that must be taken into account. This article in two parts describes the method used by the Survey Department of the Directorate-General for Public Works and Water Management (Rijkswaterstaat; The Netherlands), which for reference purposes in this article we shall call the ‘Dutch method’.<P> As explained in Part I in theprevious issue of Hydrointer­national, the alignment of the... (read more)
2009-01-05 12:00:00

Gravity Data Determines Sloping Sea Dilemma

For decades, scientists have disagreed about whether the sea is higher or lower heading north along the east coast of North America. Gravity data from ESA’s GOCE satellite contributed to settling this controversial issue. The conclusion: it is lower. Winds, currents, tides and different temperatures cause seawater to pile up in some regions and dip in others. However, it is difficult to determine relative heights of the sea, especially near the coast. To do this, tide gauge measurements need to be compared with a ‘level’ surface. Carrying surveying instruments The old method of making these calculations involved conventional levelling, carrying... (read more)
2013-02-18 12:08:01

ASL Data for Vancouver Port Authority

Vancouver Port Authority (VPA) is to expand its terminal at Roberts Bank in British Columbia, Canada, and has contracted ASL Environmental Sciences to provide long-term wave and current data for input to engineering and environmental studies. VPA purchased the necessary equipment based on ASL advice. In a novel approach, ASL designed a two-part mooring assembly to hold the Nortek AWAC instrument, which will provide the data from a depth of 8 metres. The bottom part of the mooring is deployed first and positioned with weights and the instrument assembly is then lowered onto levelling bolts on the base and attached... (read more)
2004-10-05 12:00:00

ASL to Provide Wave and Current Data for Vancouver Port Authority

Vancouver Port Authority (VPA) is looking at expanding its terminal at Roberts Bank in British Columbia, Canada. In support of this project, ASL Environmental Sciences has been contracted to provide long-term wave and current data for input to engineering and environmental studies. VPA purchased the necessary equipment based on ASL’s advice. In a novel approach, ASL designed a two part mooring assembly to hold the Nortek AWAC instrument, which will provide the data from a depth of 8 meters. The bottom part of the mooring is deployed first and positioned with weights and the instrument assembly is then lowered onto... (read more)
2004-09-06 12:00:00

Tides Workshop 2016

The Permanent Committee on Tides & Mean Sea Level (PCTMSL) Bureau in Australia has sponsored a tides workshop aimed at raising the level of tidal knowledge of those people involved in marine operations, hydrographic surveying and data collection. The workshop was conducted at the Tidal Unit, Bureau of Meteorology, Adelaide, and consisted of a mixture of theory and hands-on sessions over three days, from 16 to 18 May 2016 with a field trip on the 19 May 2016. The topics that were covered included tidal theory, storm surges and extreme events, mean sea level and climate variability, climate change and... (read more)
2016-06-06 01:19:00

Benefits of UAS Breakwater Monitoring

The North Sea Canal in The Netherlands connects the Port of Amsterdam with the sea. The two breakwaters at the mouth of the harbour in IJmuiden are usually monitored on displacement of basalt block by airborne Lidar and on subsidence by annual levelling of permanent points. Could a camera-equipped UAS survey conducted simultaneously with a bathymetric survey provide information of equivalent accuracy? A recent study has shown that it could: time series of 3D models of the breakwaters are useful for erosion and subsidence monitoring. By Pieter Franken, Skeye BV, The Netherlands Monitoring of the breakwaters at IJmuiden, The Netherlands,... (read more)
2014-08-05 10:45:21

UAS at the Beach

Merging UAS DEM and Bathymetric Depths to Monitor Breakwater Subsidence and Erosion
The North Sea Canal connects the Port of Amsterdam with the sea. The two breakwaters at the mouth of the harbour in IJmuiden, The Netherlands, are usually monitored on displacement of basalt block by airborne Lidar and on subsidence by annual levelling of permanent points. Could a camera-equipped UAS survey conducted simultaneously with a bathymetric survey provide information of equivalent accuracy? Here, the author shows that it could. Time series of 3D models of the breakwaters are useful for erosion and subsidence monitoring. Monitoring of the breakwaters in IJmuiden, The Netherlands, is currently carried out using airborne Lidar together with... (read more)
2014-07-17 02:36:42

Walney Offshore Windfarm Project Chooses Holmatro

DONG Energy, leading partner in the construction and operational phases of the Walney project, uses Holmatro's aluminium hydraulic cylinders for levelling the foundations of the turbines. So-called transition pieces (TP's) are mounted on top of monopiles driven into the seabed, together forming the foundations. The structure is fixed with a glue-like concrete called ‘grout' after which the foundation is completed. Each TP is 24 metres tall and weighs approximately 300 tons. In order to level one TP, 6 hydraulic cylinders, each with a capacity of 75 tons are needed. Holmatro's lightweight aluminium cylinders are easy to handle and corrosion resistant... (read more)
2010-09-02 10:12:29

NaviModel DTM Software

NaviModel software for ocean mapping, data analysis and interpretation provides intuitive 3D visualiasation of infinite survey data sets by import of multiple data formats and sources using user-defined templates. NaviModel includes features for data cleaning either manually or through use of advanced semi or fully automated tools as well as creation of own filters by use of plug-in function. Digital terrain models (DTM) are displayed in real-time fly-through fashion featuring different color modes and palettes in addition to adjustment of light source. Difference models and volume calculations are visualised by colouring the resulting DTM in difference modes. Terrain manipulation is... (read more)
2010-02-18 09:34:00

Tugs to Be Equipped for Dredging and Surveying Roles

Baggerbedrijf De Boer B.V. (Dutch Dredging B.V.) has ordered two custom-made, special-purpose tugs to be built at Damen Shipyards Hardinxveld in The Netherlands through the subsidiary De Boer Remorquage SARL. The larger of the two, the WID 2915, will be configured for a variety of roles including dredging using the Air and Water Injection Dredging (AIRSET) method. The smaller ASD 2310 SD (Shallow Draught) tug will be fitted out to operate the equipment needed for bed-levelling and will also carry out surveying activities. The tugs are for a 10-year contract with Grand Port Maritime de Guyane in the ports of... (read more)
2017-02-23 01:40:56
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