Bathymetry of Lake Superior 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. This project is a cooperative effort between investigators at the NOAA National Geophysical Data Center's Marine Geology and Geophysics Division (NGDC/MGG), the NOAA Great Lakes Environmental Research Laboratory (GLERL) and the Canadian Hydrographic Service(CHS). Bathymetric data have been collected from the Great Lakes in support of nautical charting for at least 150 years by the US Army Corp. of Engineers (before 1970), the NOAA National Ocean Service (NOS)(after 1970), and the Canadian Hydrographic Service. No time frame has been set for completing bathymetric contours of Lake Superior, though a 3 arc-second (~90 meter cell size) grid is available.

Bathymetry of Lake Erie and Lake Saint Clair 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. This project is a cooperative effort between investigators at the NOAA National Geophysical Data Center's Marine Geology and Geophysics Division (NGDC/MGG), the NOAA Great Lakes Environmental Research Laboratory (GLERL) and the Canadian Hydrographic Service(CHS). Bathymetric sounding data employed in compiling the one-meter bathymetry (National Geophysical Data Center, 1998) were collected over a 100-year period for purposes of navigation safety and nautical charting by the U. S. Army Corps of Engineers, the NOAA Coast Survey, and the Canadian Hydrographic Service. These bathymetric data, totaling several hundred thousand soundings, are separated four ways in existing archives: by whether they exist in digital form or reside only on paper sheets; and by whether they were collected by the U. S. or Canada. Final assembly of the new bathymetry has resulted from synthesis of bathymetric data from the four sources. Spacing of data control tracklines ranges from 500 to 2500 meters for the open lake and from 125 to 500 meters for nearshore areas. In preparation for bathymetric contouring, digital soundings were converted to metric units and computer plotted in color according to depth range. Contours in metric units were generated directly on overlays from paper sheets and then reduced to compilation scale and patched in. Compilation sheets were scanned and vectorized; and the resulting digital bathymetric contour data constitutes the primary product. The data were hand contoured by geomorphologists to capture and portray the maximum information available, resulting in a degree of detail not attainable with machine contouring and the density of available data. Bathymetric contours were prepared by geologists using sounding data contained in the paper archives at the scale of the survey sheets (scales ranging from 1: 100,000 to 1: 10, 000); or from sounding data contained in digital data bases at standard scales of either 1: 100,000 or 1: 50,000. Details concerning the methods of compilation are given in the western Lake Erie paper (Holcombe, et al., 1997). Bathymetric contours have been spatially reconciled with the NOAA Coast Survey nominal scale 1:80,000 digital vector shoreline, which by definition coincides with the Lake Erie low water datum, the zero-depth employed for bathymetric surveys and nautical charting.

Bathymetry of Lake Michigan 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. This bathymetry resolves physiography of the lake floor to an extent that known features are revealed more accurately and features never before seen are revealed for the first time. Bathymetry has been compiled using the entire array of good-quality historical hydrographic soundings collected in support of nautical charting over a 120-year period by the NOAA National Ocean Service and its predecessor agency for Great Lakes surveying, the Army Corps of Engineers. More than 600,000 bathymetric soundings were employed, of which approximately 60 per cent were already in digital form, 25 per cent were digitized in conjunction with this effort, and the remaining 15 per cent were available only on paper survey sheets. Bathymetry was compiled at a scale of 1:250,000, with a contour interval of 5 meters. Density of tracklines is generally about 2000m for the open lake and ranges from 200m to 600m for nearshore areas. Soundings collected since 1903 were already reduced to the Lake Michigan mean low water datum; these were used for bathymetric contouring without further calibration or adjustments. Soundings collected prior to 1903 were reduced to the mean low water datum. In preparation for bathymetric contouring, digital soundings were converted to metric units and plotted in color; separate colors were assigned to the various depth ranges. From the paper sheets, contours in metric units were generated directly on overlays; these contours were then reduced to the compilation scale of 1:250,000 and incorporated into the map. Compilation sheets were then scanned and vectorized; and the resulting digital vector bathymetric contour data were used to generate the imagery shown on the large color plate. Images were constructed using the publicly-available software Generic Mapping Tools (GMT).

Bathymetry of Lakes Michigan, Erie, Saint Clair, Ontario and Huron 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. Lake Superior bathymetry partially completed. The present contours and grids have been partially derived and completely compiled here at NOAA's National Geophysical Data Center (NGDC) using a variety of sources of data including the NOS Hydrographic data base and the Canadian Hydrographic Service (CHS) smooth sheets. This project is a cooperative effort between investigators at the NGDC, the NOAA Great Lakes Environmental Research Laboratory and the Canadian Hydrographic Service. Bathymetric data used for this project have been collected from the Great Lakes in support of nautical charting for at least 150 years by the US Army Corp. of Engineers (before 1970), the NOAA National Ocean Service (after 1970), and the CHS.

The National Oceanic and Atmospheric Administration (NOAA) has the statutory mandate to collect hydrographic data in support of nautical chart compilation for safe navigation and to provide background data for engineers, scientific, and other commercial and industrial activities. Hydrographic survey data primarily consist of water depths, but may also include features (e.g. rocks, wrecks), navigation aids, shoreline identification, and bottom type information. NOAA is responsible for archiving and distributing the source data as described in this metadata record.

The National Oceanic and Atmospheric Administration (NOAA) has the statutory mandate to collect hydrographic data in support of nautical chart compilation for safe navigation and to provide background data for engineers, scientific, and other commercial and industrial activities. Hydrographic survey data primarily consist of water depths, but may also include features (e.g. rocks, wrecks), navigation aids, shoreline identification, and bottom type information. NOAA is responsible for archiving and distributing the source data as described in this metadata record.

The National Oceanic and Atmospheric Administration (NOAA) has the statutory mandate to collect hydrographic data in support of nautical chart compilation for safe navigation and to provide background data for engineers, scientific, and other commercial and industrial activities. Hydrographic survey data primarily consist of water depths, but may also include features (e.g. rocks, wrecks), navigation aids, shoreline identification, and bottom type information. NOAA is responsible for archiving and distributing the source data as described in this metadata record.

The National Oceanic and Atmospheric Administration (NOAA) has the statutory mandate to collect hydrographic data in support of nautical chart compilation for safe navigation and to provide background data for engineers, scientific, and other commercial and industrial activities. Hydrographic survey data primarily consist of water depths, but may also include features (e.g. rocks, wrecks), navigation aids, shoreline identification, and bottom type information. NOAA is responsible for archiving and distributing the source data as described in this metadata record.

The National Oceanic and Atmospheric Administration (NOAA) has the statutory mandate to collect hydrographic data in support of nautical chart compilation for safe navigation and to provide background data for engineers, scientific, and other commercial and industrial activities. Hydrographic survey data primarily consist of water depths, but may also include features (e.g. rocks, wrecks), navigation aids, shoreline identification, and bottom type information. NOAA is responsible for archiving and distributing the source data as described in this metadata record.

The National Oceanic and Atmospheric Administration (NOAA) has the statutory mandate to collect hydrographic data in support of nautical chart compilation for safe navigation and to provide background data for engineers, scientific, and other commercial and industrial activities. Hydrographic survey data primarily consist of water depths, but may also include features (e.g. rocks, wrecks), navigation aids, shoreline identification, and bottom type information. NOAA is responsible for archiving and distributing the source data as described in this metadata record.