Help us improve the model
The Kwinte reference area and model are open to use for every public or private institute or company that carries out multibeam MBES measurements. Ask for the bathymetric reference model at our project partners. All interested parties can use the model, using their own tools, to calibrate their MBES setup with this well-established reference. To improve our model, we ask to provide us your entire data set. After an accurate evaluation, we will ask for approval to incorporate the results in the mean reference model calculation. The information regarding the approved survey can also be published on this website.
Only if the bathymetry meets the quality and specifications described, the backscatter data can be considered if available.
However, an accepted survey over the Kwinte area does not guarantee that all subsequent surveys with the vessel in other areas are also accepted. This is not the responsibility of the project partners.
How you can use the Kwinte reference area, what the survey requirements are and how the data will be evalueted is described further on this website.
USE THE KWINTE AREA AS A BATHYMETRIC REFERENCE AREA
Inside a subarea of the Kwinte area, a bathymetric reference model was established on the basis of the best bathymetric data collected by VH and COPCO. This reference bathymetric model makes it possible, by cross-check, to assess the hydrographic quality of the bathymetric data collected by any MBES.
In addition, due to presence of slope and targets the KWINTE area is suitable for an optimal patch test calibration (roll, pitch and heading).
The mean reference bathymetric model is only built up with surveys carried out with last generation MBESs and using RTK online corrections, which gives the highest amount of position and depth accuracy. Older surveys using tidal correction in the processing stage were omitted.
At this moment 31 surveys have been approved.
These surveys have all been processed using QINSy, QIMERA or AUTOCLEAN to create validated datasets. Different parameters are calculated and differences between each survey and the model are determined.
The image below shows an overview of the approved surveys:
Orange dots: Mean depth value of all soundings with 95% confidence error bars
Blue line: reference towards the Mean depth value of the reference model
Yellow line: reference towards the IHO Special Order Limits
A filtration of outlier soundings has been applied to the raw data, on average 85 - 95% of the soundings have been considered in this graph.
The Flemish Hydrography uses the Kwinte reference area to assess the quality of the bathymetric data from the MBESs installed on the hydrographic vessels Ter Streep and Sirius (operated by DAB Vloot).) and their multibeam setup. Moreover, Flemish Hydrography uses the area as the final test during the Acceptation Tests which every contractor has to carry out before each new contract and for each MBES and vessel that will be used.
On the image below you get an overview of the depth difference maps for each accepted survey: survey versus reference model.
By cross-checking the bathymetric data with the reference bathymetric model COPCO assesses the bathymetric quality of the MBESs installed on the research vessels Belgica I (past) and Belgica II (future) (operated by the Belgian Navy and curated by BELSPO – KBIN OD Nature) and on the Simon Stevin (operated by DAB Vloot and curated by VLIZ).
Below you see the bathymetry of the Kwinte reference area. Resolution 1x1m, vertical exaggeration VE=5x. (MBES data from RV Belgica cruise # C2012/14 EM 3002-D survey - 18/09/2012)
Inside the SE part of the Kwinte area, a subarea is proposed as a backscatter reference area. Since 2009, regular surveys demonstrate its mean backscatter level stability. Due to the uniform sandy gravelly cover, this subarea is acoustically isotropic. This is confirmed by backscatter measurements along varying directions resulting in comparable mean values and standard deviations for the same angular interval in all directions.
The Kwinte reference area can be used to assess the repeatability of backscatter measurements, necessary to ensure their quality and stability. These tests are regularly performed by COPCO as part of its monitoring of sand extraction and by RBINS - OD Nature related to their monitoring program on seafloor integrity (Marine Strategy Framework Directive; MSFD 2008/56/EC).
The backscatter level depends, among other things, on the frequency of the acoustic signal. Currently only 300kHz reference measurements are available for the Kwinte reference area. A project is underway to define a series of reference backscatter versus incidence angle curves derived from perfectly calibrated echosounders at different frequencies on the Kwinte reference area. These calibrated reference curves will be made available for every public or private institute or company that carries out MBES measurements in the North Sea and wants to calibrate its backscatter measurements.