Smithsonian - National Museum of American History, Behring Center

Physical Sciences Collection - Surveying and Geodesy

Browse Makers | Browse Instruments | Index


Photo Theodolite - click to enlarge

Photo Theodolite - click to enlarge

Photo Theodolite - click to enlarge

Click photos to enlarge.

Photo Theodolite

Catalogue number:


8 inches wide; 7.35 inches deep; 14 inches high; telescope 6 inches long

p>Photogrammetry (surveying by photographic means) came into use in the latter years of the nineteenth century, and the Bridges-Lee photo-theodolite was the first commercially available photogrammetric instrument. John Bridges-Lee (1867-1917), a science master and lawyer in London, filed two British patent applications describing this instrument in 1894, and a third in 1896, and he licenced Casella to bring it to the market. Casella was still offering instruments of this sort in the 1930s. The United States Geological Survey owned this example as early as 1899, and transferred it to the Smithsonian in 1909.

The instrument consists of a photographic camera with an internal compass card, housed in an aluminum box with a horizontal circle below, and a transit-mounted telescope with vertical arc above. The horizontal circle is graduated to 30 minutes, and read by vernier to single minutes. The vertical arc extends 90 degrees either way, and is graduated to 30 minutes and read by vernier and small telescope to single minutes. The whole instrument sits on a tribach base, suitable for mounting on a tripod.

Ref: L. Casella, Description of the Bridges-Lee New Patent Photo-Theodolite (London, 2nd ed., 1899).

Anita McConnell, King of the Clinicals. The Life and Times of J. J. Hicks (1837-1916) (York, England, 1998), pp. 98-99. This discussion of the photo-theodolite is based, in large part, on the Bridges-Lee papers, Science Museum Library Archives, London.

"The Bridges-Lee Photo-Theodolite," Engineering (Sept. 10, 1897): 312, 314-315.

C. F. Casella & Co., Ltd., Catalogue No. 564. Surveying and Drawing Instruments and Appliances (London [ca. 1937]), pp. 35-36.

Further Information: