New bathymetry has been completed for Lake Michigan, Lake Erie, and Lake Ontario and is in progress for the remaining Laurentian Great Lakes. The completed bathymetric contours were scanned and vectorized making them easily imported into GIS systems. Compilation of this bathymetry, part of a NOAA program to rescue Great Lakes geological and geophysical data, relies on the contributions of a number of geoscientists at NOAA's National Environmental Satellite, Data, and Information Service/ National Geophysical Data Center, and NOAA's Office of Oceanic and Atmospheric Research/ Great Lakes Environmental Research Laboratory, the Canadian Hydrographic Service, and several academic research centers. Wherever completed, the new bathymetry, which utilizes the entire historic hydrographic data bases of the U. S. and Canada, reveals known lake floor features more accurately and also reveals features never before seen with such detail. Consequently a new reconstruction of lake floor geomorphology is slowly emerging as the project progresses. Features seen more accurately or for the first time include drowned coastline features including headlands, spits, and large river deltas; drowned land features including river valleys and small lake beds; glaciated topography including U-shaped troughs, drumlin fields, and end moraines; extensive areas of karst topography; cuestas and escarpments formed on resistant bedrock strata; overdeepened channels resulting from wind-driven water circulation; and several anthropogenic features including dredge-spoil topography, and channels excavated by propeller wash.
As a distributable product, the bathymetry is being released in two forms: 1) a CD/DVD containing digital bathymetry and associated imagery; and 2) a color poster. The CD/DVD contains digital vector contours, the same bathymetry rasterized at a 3 arc-second grid resolution, and a selection of digital pictoral imagery. The CD/DVD's web browser interface gives access to images and to contour and grid files. The user grid access is via the GEODAS Gridded Database Software.
The color poster includes text describing the geomorphology of lakefloor features and a list of key references to previous geological literature. NGDC also produces custom imagery of Great Lakes bathymetry at any scale and projection. Underlying soundings are available on a separate NGDC CD/DVD containing Coast Survey sounding data for U. S. coastal areas and the Great Lakes.
For instructions on running the software for Great Lakes Bathymetry see Step by Step: Great Lakes Bathymetry.
Each Great Lakes Bathymetry CD/DVD contains a series of grids covering the area on the CD/DVD. Each of these CD/DVD grids is a block of 1 degree by 1 degree. The files are named according to a NGDC Id file naming scheme.
The Great Lakes Bathymetry Project grids were created using the many of the methods used in the NGDC Coastal Relief Model grids. For information see Developement of NGDC Coastal Relief Model.
For more information please see our Great Lakes Bathymetry web site at www.ngdc.noaa.gov/mgg/greatlakes/greatlakes.html