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Shelton 100-meter comparator

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

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

Army surveyor with odometer carriage.Survey of public lands...

Yolo Buggy with George Davidson.Base Line party of George...

Yolo Buggy used to transport and shade base measuring instruments...

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

Coast Survey party measuring Epping Plains Base.The last base...

Coast Survey party measuring Epping Plains Base.The last base...

Coast Survey party measuring Key Largo Base.Base Line party of...

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

Use of odometer for measuring distances

Irish Ordinance Survey baseline.First to use bi-metallic...

Measuring baseline with wooden rods.French expedition to Peru

Signal lamp and batteries

Signal lamps

Showing light at Station Northome.Battery powered lights about...

Heliotrope setup at camp of lightkeeper.Triangulation party of...

Battery-powered electric signal lamp.Triangulation party of...

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

Heliotrope being used in western United States

Signaling with heliograph near Monument 92.Alaska - Canada border...

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

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