Bathymetry of Lake Ontario

Bathymetry of Lake Ontario has been compiled as a component of a NOAA project to rescue Great Lakes lake floor geological and geophysical data and make it more accessible to the public. The project is a cooperative effort between investigators at the NOAA National Geophysical Data Center's Marine Geology & Geophysics Division (NGDC/MGG) and the NOAA Great Lakes Environmental Research Laboratory (GLERL). was compiled utilizing the entire historic sounding data base. The entire historic hydrographic sounding data base from the U.S. and Canada, originally collected for nautical charting purposes, was used to create a complete and accurate representation of Lake Ontario bathymetry. The U.S. data primarily came from the NOS Hydrographic Survey Data. This and other bathymetric sounding data collected by the U.S. National Ocean Service's (NOS) Coast Survey and the U. S. Army Corps of Engineers was employed to construct bathymetric contours at 1 meter intervals from 1-10 meters depth and 2 meter intervals at depths greater than 10 meters. Compilation scales ranged from 1:10,000 to 1:50,000. Bathymetric sounding data collected by the Canadian Hydrographic Service (CHS) were employed to construct bathymetric contours at 1 meter intervals and compilation scales ranging from 1:1,000 to 1:30,000. Digitization of the bathymetric contours, merging of the bathymetric contour data sets, poster construction, and preparation of a CD-ROM, were accomplished at the NGDC. Multibeam bathymetric data collected by the University of New Brunswick's Ocean Mapping Group (UNB-OMG), with support of the Geological Survey of Canada (GSC) and the CHS, were kindly made available in gridded form. In the two areas where multibeam bathymetric data were available, no other bathymetric data were used in the compilations. In some areas all available Canadian and U. S. bathymetric sounding data, collected at different times on different survey expeditions, were used to derive the contours. The U.S. coastline used was primarily the GLERL Medium Resolution Vector Shoreline dataset (Lee, 1998). Where needed for more coverage, the NOS Medium Resolution Vector Shoreline for the Conterminous U.S. (1994) dataset was used. Coastlines from the CHS bathymetric sounding data field sheets were used to complete the Canadian coastline. Images were constructed using the publicly-available software Generic Mapping Tools (GMT).