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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).
Diagram of measurements: D is the slant distance; S is the horizontal distance; Δh is the vertical distance. Tacheometry ( / ˌ t æ k i ˈ ɒ m ɪ t r i / ; from Greek for "quick measure") is a system of rapid surveying , by which the horizontal and vertical positions of points on the Earth's surface relative to one another are determined ...
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.
For example, a typical stadia mark pair are set so that the ratio is 100. If one observes a vertical length on a stadia rod, rule or levelling rod with the telescope and sees that the rod spans 0.500 m between the marks (the stadia interval), then the horizontal distance from the instrument to the rod is: 0.500m x 100 = 50 m.
A topographic survey is typically based upon a systematic observation and published as a map series, made up of two or more map sheets that combine to form the whole map. A topographic map series uses a common specification that includes the range of cartographic symbols employed, as well as a standard geodetic framework that defines the map ...
Being non-numeric, they are less useful to a scientific survey than contours, but can successfully communicate quite specific shapes of terrain. [2] They are especially effective at showing relatively low relief, such as rolling hills. It was a standard on topographic maps of Germany well into the 20th Century.
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.