Bathythermograph Data, Lake Michigan, 1954

In 1954 researchers at the USGS Great Lakes Science Center conducted 11 research cruises on Lake Michigan during which 779 bathythermographs were cast to collect temperature profile data (temperature at depth). Bathythermographs of that era recorded water pressure and temperature data by mechanically etching them as a curve on a glass slide. Data was collected from the glass slide by projecting the image of the curve, superimposing a grid, and taking a photo of it, thereby creating a bathythermogram. Data collection personnel could then read the data from the curve. This USGS data release is a digitized set of those original bathythermogram print photos and the temperature and depth data the project team collected from them using the open-source software, Web Plot Digitizer, as well as metadata describing each. In addition, because of their historical value as well as potential future use, this data release includes the cruise logs, which include nautical and research notes beyond the logical scope of this data release.