C&GS Chart 5101A, 1939, a prototype chart incorporating bathymetry acquired
with RAR navigation by the C&GS out to oceanic depths. This chart was meant for
navigation by following bottom contours. No other chart like this was ever
produced as WWII intervened and the use of electronic navigation systems became
widespread. The C&GS surveyed the continental margin of the U.S. by 1939.