Up on its tripod in rain, snow, and wind, the instrument was expected With salt water, the instruments were often carried across rocksĪnd up cliffs to reach the high-point location of a survey mark. Transportedįrom ship to shore in open boats, with their cases frequently splashed T-2 was especially useful for providing horizontal and vertical controlįor hydrographic surveys, which measure water depth along coasts. Observations, batteries and bulbs were substituted for the mirrors. Two adjustable mirrors provided light during the day. Glass horizontal and vertical circles internal to the instrument, theĪngular measurements were made by way of various internal prisms and couldīe read with an accuracy to one second of arc. The Wild T-2 is relatively small, light, and very rugged. Azimuth plus a radio range allowed repeated positioning of the boat Grady Tuell in this image – tracked a moving launch withĪ T-2 during hydrographic surveys, reading the azimuth every minute or Prior to the Global Positioning System (GPS), a keen observer – Lt. Image courtesy of Commander Grady Tuell, NOAA Corps (ret'd). The Coast and Geodetic Survey used the T-2 for third-order surveys. It is a relatively small, yet rugged, theodolite that could take observations both during the day and at night. The Wild T-2, shown in this image, was used throughout the 1950s – 1980s.
0 Comments
Leave a Reply. |