Hydrographic signal as seen from sea

A pole signal at Station Clarence Astro. Party off of EXPLORER

Tripod signal on south coast of American Samoa. Built by party off of SURVEYOR

Station Pic at west end of Picara Point. Building party off of WHITING

Station Pic at west end of Picara Point. Building party off of WHITING

Building signal at Station Out. Building party off of WHITING

The way to Station Can. Building party off of WHITING

Signal and navigation trisponder at Station Can. Installation by party off of WHITING

Signal and navigation trisponder at Station Can. Installation by party off of WHITING

Station Hans at south end of Hans Lollik Island. Building party off of WHITING. Note century plants and desert aspect of island

Triangular hydro signal. Building party off of PATHFINDER

Hydro signal being built for calibration of Raydist system. Building party off of NOAA Launch 1257. Glenn Hendrix kneeling, Steve Lloyd standing

Signal building party off of PEIRCE

Large tripod signal being built. Building party off of PEIRCE

Signal building party in Southeast Alaska. Party off of PATHFINDER

Signal in Prince William Sound

Signal in Prince William Sound

Signal in Penobscot Bay. Signal built by party off of PEIRCE

Dismantling the signal at Station Out, Thatch Cay. Cleaning up at the end of a project. Lt.(j.g.) Mike Kuhl cutting wire securing signal

Flags on bell and whistle buoys. Using harbor buoys for signals for survey work off the BACHE. Black flags showed up best

Planting a survey signal buoy. Off LYDONIA or NATOMA

Constructing a floating buoy signal. Buoy in place. For use by East Coast wiredrag party

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