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The interval between stadia marks in most surveying instruments is 10 mrad and gives a stadia interval factor of 100. The distance between the instrument and a stadia rod can be determined simply by multiplying the measurement between the stadia hairs (known as the stadia interval) by 100. The instrument must be level for this method to work ...
Topographer's rods are special purpose rods used in topographical surveys. The rod has the zero mark at mid-height and the graduations increase in both directions away from the mid-height. In use, the rod is adjusted so that the zero point is level with the instrument (or the surveyor's eye if he is using a hand level for low-resolution work).
Wild brand subtense bar. Another device used in tacheometry to measure distance between the measuring station and a desired point is the subtense bar. [2] This is a rigid rod, usually of a material insensitive to change in temperature such as invar, of fixed length (typically 2 metres (6.6 ft)).
This ratio is known as the stadia constant or stadia interval factor. Thus the formula for distance is D = kS. where D is distance from the telescope to the rod; k is the stadia constant; S is the difference between the rod readings at the two stadia marks; For example, a typical stadia mark pair are set so that the ratio is 100.
Stadia marks on a crosshair while viewing a metric levelling rod or staff. The top mark is at 1,500 mm and the lower is at 1,345 mm; the distance between those two marks is 155 mm, yielding a distance to the rod of 15.5 m.
A direct-readout theodolite, manufactured in the Soviet Union in 1958 and used for topographic surveying. A theodolite (/ θ i ˈ ɒ d ə ˌ l aɪ t /) [1] is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes.
The complete unit is normally mounted on a tripod, and the telescope can freely rotate 360° in a horizontal plane.The surveyor adjusts the instrument's level by coarse adjustment of the tripod legs and fine adjustment using three precision levelling screws on the instrument to make the rotational plane horizontal.
Survey markers, also called survey marks, survey monuments, or geodetic marks, are objects placed to mark key survey points on the Earth's surface. They are used in geodetic and land surveying . A benchmark is a type of survey marker that indicates elevation ( vertical position ).