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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. In the adjacent image, the upper stadia mark is at 1.500 m and the lower at 1.345 m.
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 ...
Surveyor's view of the levelling rod with the crosshair. This indicates a reading of 1.422 m, interpolated between the 1.420 m and 1.430 m marks. Rods come in two classes: Self-reading rods (sometimes called speaking rods). Target rods. Self-reading rods are rods that are read by the person viewing the rod through the telescope of the instrument.
The cross hairs are used to establish the level point on the target, and the stadia allow range-finding; stadia are usually at ratios of 100:1, in which case one metre between the stadia marks on the level staff (or rod) represents 100 metres from the target. The complete unit is normally mounted on a tripod, and the telescope can freely rotate ...
This is converted to distance from the instrument to the stadia rod by multiplying the stadia interval by the stadia interval factor. If the stadia rod is not at the same elevation as the instrument, the value must be corrected for the angle of elevation between the instrument and the rod. The formula most widely used for finding the distances is:
The rod, perch, or pole (sometimes also lug) is a surveyor's tool [1] and unit of length of various historical definitions. In British imperial and US customary units, it is defined as 16 + 1 ⁄ 2 feet, equal to exactly 1 ⁄ 320 of a mile, or 5 + 1 ⁄ 2 yards (a quarter of a surveyor's chain), and is exactly 5.0292 meters.
The Y level or wye level is the oldest and bulkiest of the older style optical instruments. A low-powered telescope is placed in a pair of clamp mounts, and the instrument then leveled using a spirit level, which is mounted parallel to the main telescope. The term dumpy level (also builder's level) endures despite the evolution in design. They ...
The rod is used in levelling procedures to determine elevations and is read using a level. A Philadelphia rod consists of two sliding sections graduated in hundredths of a foot. On the front of the rod the graduation increasing from zero at the bottom. On the back of the rod the graduation decrease from 13.09 ft at the bottom to 7 ft.