Alignment

from Wikipedia, the free encyclopedia

As alignment , alignment or Alignement [ a.li.ɲə.mɑ ] ( French for "orientation", "straight set", "building line") is in the measurement of the alignment of points along a straight line and warding in a straight line designated . The alignment here is the straight line or the arrangement in a straight line. Alignment is the placement of individual points such as alignment rods in a straight line, the start and end points of which are indicated. Aligning stands for aligning multiple points along a straight line (aligning a straight line), but is sometimes used to lengthen a straight line.

When aligning, generally only the horizontal deviation from the reference line is considered. Strictly speaking, points are therefore aligned in a vertical plane. The procedures range from aligning with leveling rods and the naked eye, to using a theodolite, to special alignment or alignment instruments. In the case of deformation measurements , the determination of small deviations from a reference line is also an object of alignment.

In mechanical engineering , the precise alignment of components by aligning them often also means the uniform support of axes . Misalignment z. B. small bumps can cause wear on machines and production errors. In craft escapes also plays a role, for. B. when screwing in countersunk screws, when fitting individual wooden parts of furniture or flat elements such as external cladding in house construction.

The deck bearing in shipping is an alignment in which a line of two markings is extended.

Alignment with alignment poles

The end points of the straight lines are indicated by vertical alignment poles. Then you aim from the starting point to the end point and point a third rod so that it is in the straight line. If several points are to be aligned in a straight line, start with the most distant point. Plumb lines can also be used for short distances .

With the naked eye, measuring lines up to 200 m long, accuracies of 2 to 3 rod thicknesses can be achieved. With an angled prism , it is possible to align yourself between two signaled points without a second man. For higher accuracy requirements or for steep or undulating terrain, a theodolite should be used, which is set up on one point on the straight line and whose direction is set to a second point on the straight line.

Alignment is used in cadastral surveys using the orthogonal and integration method or in construction to mark out straight lines, to create intersections of straight lines or to re- measure points. If points are to be measured to the side of the aligned straight line, the plumb point in the straight line (measurement line) is determined with an angled prism so that there is a right angle .

Mechanical alignment

With mechanical alignment, the straight line is created using a cord or wire that is stretched and centered over the end points. In construction, the used polishing sometimes for an elastic shock cord . With a little chalk the whole line can be marked with it. The upholsterer also marks lines of the same height.

With nylon cords an accuracy of 2 mm can be achieved on lengths up to 25 m, with wires and wire tensioning devices it can be less than 1 mm on longer lengths. Since cords or wires are influenced by the wind, this method is not suitable in the open air with high accuracy requirements. B. for monitoring inside dam walls. Changes can be recorded continuously with electrical sensors.

Optical alignment with telescope

Theodolites or special alignment instruments are used for higher accuracy requirements . Applications of engineering geodesy are deformation measurements or industrial metrology. The instrument is set up on a point on the straight line and set on a target mark. Then intermediate points are aligned or - especially in the case of deformation measurements - their lateral deviation is determined.

Aligning instruments do not have pitch circles , but they do have a telescope that can be enlarged and tilted. During deformation measurements, moving target characters are moved into the target beam at the measuring points. The size of the shift indicates how the measuring point has moved. A measurement accuracy of less than 1 mm for a 400 m long line can be demonstrated. There are also alignment instruments that measure the horizontal deviation with a flat-plate micrometer .

Alignment with laser

Laser alignment is the staking out of a straight line with the help of a visible laser beam . The laser beam can be adjusted horizontally, vertically or with the desired inclination and fixed for the duration of the work. The alignment can thus be determined or checked at any intermediate point on the straight line at any time directly at the building site. Lasers are particularly useful in poor visibility (e.g. darkness), and a second person is not required at the laser for instruction. Laser devices are well suited for the control of construction and tunneling machines in traffic route, line and tunnel construction.

A reference plane can also be realized by fanning out the beam. A horizontal reference plane can be used for leveling tasks, a vertical one is suitable for plumbing and alignment.

Alignment with obstructions

When setting out straight lines in the terrain, it can happen that there is no continuous line of sight from the start to the end point. Special procedures have been developed for such cases.

The mutual warding or Einfluchten is applied when both endpoints are not accessible (eg. B. house corners) or are not mutually visible due to a rise in the ground. For this purpose, two alignment poles 1 and 2 are placed approximately in the connecting line A - E to be staked out, so that it is divided into approximately three equal parts. Then, one after the other, rod 1 is aligned in line A – 2 and rod 2 in line 1 – E until there are no more changes.

If an old measurement line is built in or overgrown, it can be removed . For this purpose, a parallel measurement line is formed at a certain distance into which intermediate points are aligned. The offset dimension must be measured back from these intermediate points in order to obtain an intermediate point of the original line.

With modern total stations or satellite geodetic methods ( GPS ), points of a straight line can be staked out, the end points of which are known in terms of coordinates. To do this, a point is measured, the deviation from the straight line is calculated and the position is then corrected until it lies precisely enough on the straight line. When setting out a building on a batter board , it can be set out from an instrument standpoint.

literature

Web links

Wiktionary: alignment  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ Entering and escaping in this sense used in: Heribert Kahmen: Vermessungskunde I. 17th edition. de Gruyter, Berlin / New York 1988, p. 51f.