Centering (geodesy and mine surveying)

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In geodesy and mine surveying, centering or centering is the precise setting up of a measuring instrument over the reference or measurement point .

Centering is particularly necessary for instruments that are used to take direction or angle measurements (such as theodolite and total station ), GNSS receivers, plummet instruments and photogrammetric cameras . When free up where convenient centering account for more than one fixed point.

The centering can with a plumb line, a range pole or an optical plummet done. When using an optical plummet, the tripod with the measuring instrument is initially set up approximately over the center of the point on the ground. In the second step, the optical plummet is adjusted to the center with the foot screws. Then the tripod legs are extended and pushed in so that the measuring instrument is roughly leveled. The fine leveling is then carried out with the foot screws of the tripod. Since the optical plumb line can move out of the center again, the measuring instrument must finally be moved on the tripod plate until the optical plumb line points back into the center. During this movement, the tripod with the measuring instrument must not be rotated in relation to the tripod plate, otherwise the leveling will be lost.

With the help of forced centering , measuring instruments and target boards or reflectors can be exchanged while maintaining the centering.

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