Put simply, a bathymetric chart is a form of thematic map depicting submerged topography, just as topographic maps depict terrestrial topography. This is usually accomplished by means of contour lines, often augmented by differential shading or coloring to highlight variations in depth. The earliest bathymetric charts were based on compilations of hundreds or thousands of individual soundings, taken by the ancient, muscle-powered technique of lowering a weighted, graduated line to the sea bottom. The field was revolutionized by the advent in the 1930s of systems using sound (sonar) and later in the 1960s light (LIDAR), which vastly enhanced the amounts and accuracy of data that could be gathered.
Offered here is a spectacular example of the genre, roughly three feet square and using color to delineate the spectacular undersea topography of the Pacific Basin. Terrestrial and undersea topography are shown in 1000-meter increments, from white in the snow-capped High Andes to pitch black in the Marianas Trench, at 10,865 meters the lowest elevation on Earth. The decorative impact of the image is greatly enhanced by painterly renderings of undersea topography in the corners, including craters, valleys and canyons as or more spectacular than anything known above water.
A note to the left of the title informs the viewer that the map is “Based on chart in “Marine geology of the Pacific”, by H.W. Menard”. Published in 1964, Menard’s work was the first synthesis of research conducted in the past two decades, yielding a “vast amount of information concerning the Pacific Ocean … acquired in the fields of bathymetry, seismic exploration, gravity, magnetism, heat flow, petrology, and volcanism”. (review in Science, vol. 146, issue 3643 (Oct. 23, 1964), p. 513)
If I am reading the historical record correctly, the bathymetric chart was a promotional piece of sorts, produced in 1965 by the Deep Submergence Systems program of Autonetics, at the time a division of North American Aviation developing guidance systems for submarines and ICBMs. The program was a response to the Deep Submergence Systems Review Group established by the Navy in 1963, after the loss of the USS Thresher off Cape Cod and an H-bomb off Spain revealed the inadequacy of its “deep ocean capabilities”. The title block indicates the map was “made available” by A. B. Rechnitzer and R. D. Terry. Andreas B. Rechnitzer (1924-2005) was a legendary diver and pioneer in the development and use of deep submersibles by the Navy. His colleague R. D. Terry seems to have been less prominent but was well published in the field of deep submersibles.
OCLC lists numerous institutional holdings, but as of August 2021 an internet search turns up no examples currently offered for sale or any record of its having appeared on the secondary market.
OCLC 5501495 et al. For background on Rechnitzer, see “Obituary: Andreas B. Rechnitzer” at SeaDiscovery.com.