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Integrating multiple data sources, using GIS

A large amount of new data is generated by MAR-ECO. Using their own methods, specialists gain new exiting information from the datasets. But even more information can be found when combining information from different dataset - like combining depth and fish catches might reveal that some fish species prefer deep water.

By Helge Astad

GIS (Geographical Information Systems) is software that handles many kinds of data ordered by geographic location, unlike other such systems. Using GIS on the research area of MAR-ECO, provides views that emphasises on different features from the cruises. Scientists can recreate these views adding own data to see how they interact with the surroundings.

Image 1)An overview of the area

To get an overview of the area, several datasets from MAR-EO can be used. New datasets can be created, or free datasets from the Internet can be used as a framework to place other data on top of. 

In image 1) two datasets has been used: A bathymetry layer showing sea depths and another layer showing the outline of the countries around the North-Atlantic. Handled by GIS, the geographical information in the data layers overlap seamlessly.

Image 2)A three dimensional view, which might be easier to understand, can also be created with GIS. In image 2) we can see the North Atlantic with bathymetry and outline of the surrounding countries. The red points are the positions of the ROBIO lander and the line is the cruisetrack of G. O. Sars. The 3D view is useful as it provides an overview of the entire area, but it requires a solid computer to be able to work with 3Ds.

Image 3)A closer look

When the datasets allows, zooming in can reveal more details of the area. Like in image 3), where we can see detailed bathymetry from an area with five ROBIO lander sites centered along the 52 N longitude.

A ROBIO lander is a device that is lowered to the seafloor and consists of 500 g mackerel, some weights, a camera and some other equipment. The scent of the mackerel attracts other fishes, and the camera takes a picture every 90 seconds. A signal from the research vessel releases the weights so the lander can return to the surface, where the images are inspected and the number of species are counted. Nicola King from the University of Aberdeen has been writing a Phd. on this subject, finding among else how different species of fish are distributed according to depth, longitude and distance from land.

Image 3)GIS can also be used to illustrate the currents speed along the bottom, as denoted by the arrows in image 4). We can see how the water streams from east to west over the ridges of the Mid-Atlantic Ridge. The values are output from the ROMS model run by IMR in Norway. The data is from day 200, 2004, which is the same as July 18, 2004.
This can also be shown in 3D. The combination of both current directions, bathymetry and the positions of the ROBIO lander can be useful for scientists who wants to know more about the conditions locally around the ROBIO lander sites.

Image 5)A detailed view

The closest view is of bathymetry collected by echosounders, which measures the depth in great detail. This is large datafiles covering a small area.

The same ROBIO lander site is visible in image 5) as well, we can see it laying in a sort of ravine facing the 900 m steep cliff going up in the west.

Image 6)The distance from the landing site to the nearest ridge is about 800 m, with a difference in depth ranging from -1980 m at the landing site to -1890 m at the ridge. The steep wall is about 5 km away and goes all the way up to -1150 m.

The additional information given by the bathymetry and the general currents in the area can be very useful for the scientists working with the data from the ROBIO lander, telling them about where the scent goes and where the fishes may originate from. Other scientists can also get additional information from other sources and visualize them with GIS to help them see the environment surrounding their data.

Sources

H. P. Astad, 2005: Marine Data Integration - Satellite images, in-situ data and numerical ocean models in GIS

Most of the data presented is from MAR-ECO. Other sources include:
U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Geophysical Data Center, 2001. 2-minute Gridded Global Relief Data (ETOPO2) 

IOC, IHO and BODC, 2003. Centenary Edition of the GEBCO Digital Atlas, published on CD-ROM on behalf of the Intergovernmental Oceanographic Commission and the International Hydrographic Organization as part of the General Bathymetric Chart of the Oceans, British Oceanographic Data Centre, Liverpool, U.K.

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