Level staff
The leveling is a term used in geodesy scale. It describes the vertical distance between the horizontal beam of the target Nivellierfernrohrs and the point of the bar and are primarily the geometric leveling before the vertical scale. In addition, it serves as a destination point for an exact horizon patented instrument, the leveling instrument.
- 3.1 Faulty circular level
- 3.2 Zero error
- 3.3 Aufsetzflächenfehler
- 3.4 Staff graduation
- 3.5 Other effects of errors
Introduction
In general leveling staffs of dried pine or ash are produced, even a metallic construction is possible. Its shape is rectangular with a width of 6-9 cm and a height of usually 3-4 m. Furthermore, often ribs are attached for stiffening and protecting the Staff graduation. There are grab handles, designed to improve handling on both sides of the bar. The versions of the leveling rod are very versatile: Collapsible, to assemble from individual segments or as a telescopic bar. An oil paint and weather resistant paint to protect against moisture, a metallic leg attaching tool perpendicular to the longitudinal axis bar with a flat seating surface from damage and he sets the zero point.
Types / designs
Depending on the nature and objective of using different leveling rods are used. They differ in terms of their scale division, material use and the achievable accuracy of the reading.
Two scales Latte
Bar code
Simple bar (DIN 18703 )
The simple bar is distinguished by its relatively simple field placement. Large Arabic numerals at the beginning of the associated field characterize the dm- classification. Within a clause is illustrated by thicker lines the cm scale. Between these the millimeter can only be determined by estimation. The color changes, usually red / white or black / white, reduced gross reading errors. The metrical organization of the slat is referred to as e- division by their appearance, hence the name E- bar. As a result of irradiation may lead to errors in the estimation of a millimeter. White on black cover basic act by more than black on white. This effect is, in other embodiments simple battens counteracted by the checkerboard spacing.
Precision bar (DIN 18717 )
When precision leveling special precision battens must be used. They also have a frame of wood or light metal, but a Invarband with 200 N tensile force is in contrast to simple slats clamped. This achieves a high resistance to length changes due to temperature fluctuations. Next enhancing accuracy is the effect of a more differentiated scale division. On the one obtained by the ½ cm scale a more accurate reading, on the other hand allows the use of two mutually staggered double scale readings that serve the reading control.
Digital Levels used to determine the height reading no analog numbers that are applied to the bar. As the name suggests, the measured value is generated by digital signal processing. Accordingly, the leveling rods must be adjusted. They are also provided with a Invarband on which a manufacturer-specific binary code is applied (See barcode). The reading is done now by comparing the visible through the telescope bar sector with an internally stored image of the bar.
Errors and elimination
Faulty circular level
To check the circular level on the leveling rod, a suspended solder is used. This allows the exact locations of the vertical bar. If the bubble of the circular level not settle in the middle, they can be aligned accurately with the adjustment screws.
Zero error
When attaching the steel block or after frequent placement of the leveling it may happen that the underside of the bar no longer exactly corresponds to the zero point of the bar disposition. If only one bar in the course of leveling is used, the constant errors due to the subtraction of back - and foresight is eliminated. If you work with two slats, this deviation can be eliminated by an even number of instrument lineups. If this is not possible, the zero-point error must be determined and applied to the measurements. For this purpose several staff setups are used that are visible from an instrument standpoint. Well, any of the two slats are successively placed on all slat base rates and the heights are read by horizontiertem leveling. From the differences between the corresponding readings at two slats of the zero-point error can be determined.
Aufsetzflächenfehler
Similar to the zero-point error, it may happen that the contact surface is not flat and not perpendicular to the bar classification. For checking the bar is 7 points, which are distributed over the contact surface, is placed. It should be noted that the center must be included. The differences between the staff readings for borrowing position now indicate an unevenness of steel pedestal. When leveling is it to ensure the bar is always at the center of the contact surface be placed on the pedestal,.
Staff graduation
The review of the Latte classification has to control the goal of the inner pitch accuracy and the absolute length of the bar meter. Due to inaccuracies in the production of bar, it may happen that the vertical division has deviations from the cm intervals and this also increases linearly with the division bar. These systematic deviations play a role only at the highest accuracy and precision leveling and high altitude. The investigation of the bar classification is performed using a benchmark or a Komparatorbahn with interferometer.
Other error sources
Further inaccuracies at work with a leveling caused by the deflection of the bar, defective locks and hinges with a folding propeller and loose Fußbeschläge. However, this can only be avoided by careful handling and storage of the bar.
Accessories
The Latte Shoe guarantees that the leveling rod is always placed at the same point of the contact surface on the frog. This avoids that Aufsetzflächenfehler negative effect on the measurements.
Become an indispensable accessory when working with Levelling heard the frog. He " liked " a fixed point and insured within the geometric leveling halting of the same point upon rotation of the bar.
For precise leveling and difficult wind conditions support rods can be used to increase the stability. They cause a strong reduction of the vacillation of the bar and are therefore accuracy -enhancing.
Probably the most important tool that belongs in every case for leveling and is mostly grown firm, is the circular level. It allows vertical installation of lath and decisively influenced the accuracy and the success of the geometric leveling.