transittheodolites

A transit theodolite is a type of EDM (Electronic Distance Measurement) device used in geodetic surveying to measure the distance and direction between two points. It is a hybrid instrument that combines the functionality of a theodolite, which measures horizontal angles and vertical angles, with a transit, which is a rotating beam that shines a beam of light over the observation points.

Transit theodolites are used to determine the relative position of a series of reference points on the earth's surface. They are commonly used for triangulation surveys and GPS-free positioning, particularly in areas where GPS signals are weak or unavailable. The instrument measures the angle between a line of sight, for example, to a reference mark, and determines the horizontal distance from the theodolite to the reference mark.

Transit theodolites generally consist of an inner transit telescope, an outer telescope, and a rotating circle. The inner transit telescope measures the vertical angles, while the outer telescope measures the horizontal angles. The rotating circle is divided into angles and is used to determine the direction of the line of sight. Some modern transit theodolites are using electronic distance measurement technology to improve the accuracy and speed of measurements.

Typical components of a transit theodolite include an optical telescope, a leveling system to ensure accurate vertical angles, and a prismatic table to support the transit telescope. Other features, such as graduated circle, electronic distance measurement system, and tilt sensor, can be present depending upon the model. Transit theodolites have been used for many decades for precise measurements in geodesy and surveying.