Bathymetric Mapping


Coastal environments are some of the most dynamic and constantly changing regions of the globe. Monitoring and measuring these changes is critical to marine navigation and for construction of harbors, pipelines and other critical infrastructure in the coastal zone or shallow off-shore areas..

One of the most important parameters is information about water depth. In many parts of the world existing nautical charts are not accurate enough. Traditional methods include echo sounding and mapping using multi-beam sonar instruments but the cost of this type of survey is high.

GRAS has developed a cost-effective method for bathymetric mapping based on high resolution satellite images. The approach exploits the fact that different wavelengths of light are attenuated by water to differing degrees and with the newest generation of satellite this technology can be applied to map bathymetry in water down to 25-30 meters in depth under optimal conditions.

And with the addition of ground truth measurements for local calibration of the method, vertical accuracy better than 1 meter can be achieved.

Key benefits

  • Data can be obtained for anywhere on Earth
  • Cost effective solution
  • Mapping down to 25-30 m depth
  • Other features such as sea bed type and aquatic vegetation can be mapped from the images as well
  • Possible to revisit areas of interest frequently to monitor changes
  • Does not require flying or sailing permits

New satellite technology
WorldView-2 from DigitalGlobe is the first commercial high-resolution satellite to provide 1.84 m resolution multi-spectral imagery, plus a Coastal Blue detector focused on the 400 – 450 nanometer spectral range. With the Coastal Blue band included it is be possible to calculate depths up to 20 m and potentially as deep as 30 m, by measuring relative absorption of the Coastal Blue, Blue and Green bands.

Archive data or new collection of images
The mapping can be based on satellite images that already exist in the archives. An initial screening for images with good water clarity will be performed. If no suitable images exist, a new acquisition of high resolution images will be acquired. In close collaboration with satellite operators, GRAS will seek to get the best images quality that will enable accurate mapping.

Accuracy
The accuracy of the mapping depends on local conditions. In cases with optimal water quality and visibility, vertical accuracies better than 1 m can be achieved. Horisontal accuracy is within 5 m according to DigitalGlobe specifications.

Bathymetric mapping can also be done with other satellites with depth penetration down to 15-20 m.

Read more in this article from GEOconnexion, where GRAS was featured.
Please contact GRAS for further details and quotes on bathymetric mapping.