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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).
The level must be horizontal to get a valid measurement. Because of this, if the horizontal crosshair of the instrument is lower than the base of the rod, the surveyor will not be able to sight the rod and get a reading. The rod can usually be raised up to 25 feet high, allowing the level to be set much higher than the base of the rod.
Stadia marks on a crosshair while viewing a metric levelling rod. The top mark is at 1.500 m and the lower is at 1.345 m. The difference between the rod readings is 0.155 m, yielding a distance to the rod of 15.5 m. A typical surveyor's instrument reticle has two pairs of stadia marks. One pair are on the horizontal centreline and the other on ...
A Philadelphia rod is a level staff used in surveying. 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 ...
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 ...
An Ordnance Survey cut mark in the UK Occasionally a non-vertical face, and a slightly different mark, was used. The term benchmark, bench mark, or survey benchmark originates from the chiseled horizontal marks that surveyors made in stone structures, into which an angle iron could be placed to form a "bench" for a leveling rod, thus ensuring that a leveling rod could be accurately ...
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Instruments used in surveying include: Alidade; Alidade table; Cosmolabe; Dioptra; Dumpy level; Engineer's chain; Geodimeter; Graphometer; Groma (surveying) Laser scanning; Level; Level staff; Measuring tape; Plane table; Pole (surveying) Prism (surveying) (corner cube retroreflector) Prismatic compass (angle measurement) Ramsden surveying ...