Signal off the Delaware coast. Planted by RANGER

A floating signal. Photograph in 1931 Hydrographic Manual

Floating signal off the Delaware coast. Party off of RANGER

Tautwire measuring machine. By trailing wire astern and counting revolutions, one can determine distances. Used to measure distance between floating hydrographic signals

White-washed hydrographic signals in Taku Inlet area. Who says engineers can't be artistic? Signal made by crew off of WESTDAHL

ORCA signal in Taku Inlet. Told tourists in area that signals were native hieroglyphics. Signal made by crew off of WESTDAHL

White-washing hydrographic signals in Alaska.

Signal party white-washing rock. Party off of EXPLORER

White-washing rock. Party off of LESTER JONES

Preparing white-wash for marking signal. At Station ACT on Amchitka Island. Party off of EXPLORER

Taking sextant angles for positioning vessel.

Working together for a three-point sextant fix. Note horizontal attitude of sextants

Calibrating Raydist by using three-point sextant fix. Initial tests of Raydist off of SOSBEE

Launch hydrography three-point sextant fix. Surveying lagoon at Kwajalein Island. Party off of PIONEER

Launch hydrography three-point sextant fix. Surveying in vicinity of Kalgin Island. Party off of SURVEYOR

Wharton and Jeffries taking three-point sextant fix. Surveying in vicinity of Kalgin Island. On SURVEYOR

Taking three-point sextant fix with check angle. Calibrating electronic navigation system. Third man searching for signal. On NOAA Launch 1255

Taking three-point sextant fix with check angle. Calibrating electronic navigation system. On NOAA Launch 1255

Checking index error of sextants prior to conducting launch hydrography.

The tools of the trade for navigating during launch hydrography. Metallic and plastic three-arm protractors for plotting three-point fixes. Sextant in background. 1931 Hydrographic Manual

Checking boatsheet during wiredrag survey of Mitchell Jordan Reservoir. Plastic three-arm protractor for plotting fixes barely visible under hand. Surveying reservoir for seaplane landing site during WWII ferrying operations. Wiredrag party of Max G. Ricketts

Plotting three-point sextant fix with metallic three-arm protractor. On the FATHOMER

Manual plotting of three-point sextant fix. Using plastic three-arm protractor

Geometry of the three-point sextant fix. Diagram shows shoreline, stations, and angles measured. 1931 Hydrographic Manual

Graphic of various combinations of strong and weak three-point fixes. Hydrographic Manual

Graphic demonstrating Radio Acoustic Ranging (RAR). Developed in 1923, RAR was the first non-visual navigation system. Combined velocity of sound in water with radio to obtain fix.

Planting a hydrophone anchor with the cable attached. On the GUIDE. Hydrophone would pick up sound from RAR TNT explosion.

Cable drum being pulled by horses across dunes. Cable lead to offshore hydrophone for Radio Acoustic Ranging. On the GUIDE

Electronics setup for Radio Acoustic Ranging shore station. Navigation station for the GUIDE

Planting anchor for Radio Acoustic Ranging hydrophone. Must have been warm - note bare foot helping push anchor away from ship

A new type of hydrophone block for Radio Acoustic Ranging. On the GUIDE

Transferring the hydrophone block and cable to launch for planting. Radio acoustic ranging operations on the GUIDE

Launch laying the cable from hydrophone to the shore station. Radio acoustic ranging operations on the GUIDE

Shore Radio Acoustic Ranging Station on San Clemente Island. Radio acoustic ranging operations on the GUIDE

Radio operator at work at Radio Acoustic Ranging shore station KGHS. Radio acoustic ranging operations on the SURVEYOR

The first Odessey Protractor. This instrument was used to plot intersecting ranges from two RAR stations. Invented while Herman Odessey attached to DISCOVERER. Variations of this instrument were used for plotting positions for over 60 years

Radio Acoustic Ranging bomb making. TNT bombs were sound source for RAR. RAR work on OCEANOGRAPHER

Radio Acoustic Ranging bomb making. TNT bombs were sound source for RAR. RAR work on OCEANOGRAPHER

Radio Acoustic Ranging - igniting the bomb and timing fuse. TNT bombs were sound source for RAR. RAR work on OCEANOGRAPHER

Timing the fuse on a quart bomb during RAR operations. TNT bombs were sound source for RAR. RAR work on OCEANOGRAPHER

Quart bombs exploding during RAR operations. TNT bombs were sound source for RAR. RAR work on OCEANOGRAPHER

A schematic view of RAR and echo-sounding. Diagram in public information brochure

The Launch PRATT - an RAR hydrophone boat. Worked as station boat while HYDROGRAPHER conducted sounding operations

A sono-radio-buoy developed to eliminate need for station boats. RAR operations in the Gulf of Mexico. Forerunner of Anti-submarine warfare sonobuoys

Electronics package of sono-radio-buoy for RAR. This instrument was developed by Almon Vincent on the GUIDE. Forerunner of Anti-submarine warfare sonobuoys

Sono-radio-buoy for RAR work on pier --- Almon Vincent design. Forerunner of anti-submarine warfare sonobuoys

Almon Vincent tuning the antenna circuit on sono-radio-buoy. RAR work on the GUIDE

Railroad car couplers used to anchor RAR hydrophone. On the OCEANOGRAPHER

Vincent type sono-radio-buoy being deployed from the GUIDE. RAR operations on north coast of Unimak Island

Sono-radio-buoy developed by Almon Vincent for RAR work. Buoy deployed from the GUIDE