Triangulation station in shoal water. Combined operations party of Hubert A. Paton

Setup in marshy land. Traverse party of G. C. Mattison

Observer Atridge at Station Hackberry. Triangulation party of Wilbur Porter

Observing stand in western Nebraska. Triangulation party of Wilbur Porter

Observing stand in western Nebraska. Triangulation party of Wilbur Porter

Observing in western Nebraska. Chase, Smith, and Nicodemus. Recorder sitting and writing down angle observations. Triangulation party of Wilbur Porter

Observing in western Nebraska. Chase, Smith, and Nicodemus. Recorder sitting and writing down angle observations. Triangulation party of Wilbur Porter

Observing at Station BAIN 1905. Combined operations party off WESTDAHL

William Russell observing. Combined operations party off LYDONIA

"O" party on 103' tower in Missouri. Triangulation party of Carl Aslakson

Observing party on Washington Monument. Took advantage of scaffolding from 1934 cleaning of monument.

Observing from station Tiger South. Triangulation in support of aerial photography. Triangulation party of Harold J. Oliver

Map showing status of triangulation as of 1937.

Observing tent on Sequam Island. Note wind causing billowing tent

Triangulation observations on Cape Prince of Wales. The westernmost point of North America. Triangulation party of A. Newton Stewart

Observing at Station Rusty following 1964 Alaska earthquake. Station elevation subsided at least 12' during quake. Party off of HODGSON

Wild T-3 theodolite.

Wild T-3 theodolite in use. riangulation Station "CASTLE" , Westchester County, New York. The observer is Dan Novak and the other person is E. Dean Wegner. Chief of Party G-19 was James L. Cook. The station is on the Terrytown Castle.

Burt Wilhelm observing at Kelp Bay. Off of FAIRWEATHER

Triangulation work in Virgin Islands National Park. Party off of PEIRCE

Dennis Wegenast observing with Wild T-3. Transcontinental Traverse Party of Woodrow Johnson

Wild T-3 at twilight. Transcontinental Traverse Party of Woodrow Johnson

Heliograph at Station 22. Alaska - Canada border. International Boundary Commission

Signaling with heliograph near Monument 92. Alaska - Canada border. International Boundary Commission

Heliotrope being used in western United States

Light reflecting from heliotrope. Triangulation party of William M. Scaife

Battery-powered electric signal lamp. Triangulation party of William M. Scaife

Heliotrope setup at camp of lightkeeper. Triangulation party of William M. Scaife

Showing light at Station Northome. Battery powered lights about 110 feet above ground. Triangulation party of Carl Aslakson

Signal lamps

Signal lamp and batteries

Measuring baseline with wooden rods. French expedition to Peru

Irish Ordinance Survey baseline. First to use bi-metallic compensating principal for base line measurement

Use of odometer for measuring distances

Land surveyor using odometer in United States. A private county surveyor

Coast Survey party measuring Key Largo Base. Base Line party of Alexander Dallas Bache

Coast Survey party measuring Epping Plains Base. The last base line measured by Bache. Base Line party of Alexander Dallas Bache

Coast Survey party measuring Epping Plains Base. The last base line measured by Bache. Base Line party of Alexander Dallas Bache

Graded road made to measure Epping Plains Base. Base Line party of Alexander Dallas Bache

Yolo Buggy used to transport and shade base measuring instruments. Yolo Base Line, one of the most accurate measured in the Nineteenth Century. Base Line party of George Davidson

Yolo Buggy with George Davidson. Base Line party of George Davidson. The last time such buggies were used was in 1962

Army surveyor with odometer carriage. Survey of public lands. Odometer worked fairly well on flat ground

Shelton 100-meter comparator -- Making contact. William Bowie on left

At work with No. 17. William Bowie in center with white hat

Shelton 100-meter comparator

Running levels along the Stanfield Base. Base line and astro party of C. V. Hodgson

Measuring base with Invar tape. Tape underway. Base line and astro party of C. V. Hodgson

Off to measure a base with Invar tape. Party of C. G. Quillian

Time and tide waits for no man. Base line measurement in southeast Alaska. Party of C. G. Quillian

It sure is tough to stay dry with the tide coming in. Base line measurement in southeast Alaska. Party of C. G. Quillian