Humboldt State University
Robert A. Paselk Scientific Instrument Museum
A. Lietz Co.
Humboldt S-T-C; c.1925
The alidade is used with a plane table in making convenient and direct surveys. Plane table surveying has continued in use since the late sixteenth century due to its simplicity. Initially a simple rule with a couple of plain sites served as an alidade. In use the plane table is mounted on a ball joint for leveling and oriented with a compass, frequently part of the alidade as in this example. A sheet of paper is secured to the table and an initial staion indicated on the paper. A sighting is made with the alidade and the line of sight is marked on the paper. The table is then moved to another station at a measured distance, oriented with the compass, and a second sight line is taken and drawn. Sighting the same targets results in intersections on the paper cooresponding to the targets.
An oval brass tag, attached with brass pins to the top of the mahogony case, is stamped: HUMBOLDT S-T-C / 555.