Appears to be Texas Tower #4 south of Woods Hole. This tower was lost on January 15, 1961, during a storm with a loss of 28 lives. Ship was probably using tower as a fixed point to calibrate electronic navigation system.

Hydrographic signal on the shores of the reservoir of Grand Coulee Dam. Used as signal for navigation by three-point sextant fix.

VAM-2 Magnetometer installed in Navy R5D aircraft. L to R, , Mr. Robert Seaton of Navy Hydrographic Office, and L. Hurwitz, LCDR David Whipp, R. Gebhardt, Joel Campbell, and J. Bottum, all of the USC&GS.