Leveling is ... Trigonometric leveling. Types of leveling

Leveling is a type of geodetic measurement. Using it, the relative heights of various points on the earth's surface are found. As a conditional level in such measurements, natural objects such as rivers, seas, oceans, fields or other starting points can take over. In fact, leveling is the determination of the value of the excess of the surface of each object over a given (reference) one. Such measurements are required to compile an accurate terrain of the studied terrain. In the future, these data are used when drawing up terrain plans, maps or for solving specific applied problems.

What kinds of leveling exist?

Such measurements can be carried out in a variety of ways, differing by the equipment or technology used. Consider what are the main types of leveling. The most common are five methods: geometric, trigonometric, barometric, mechanical and hydrostatic measurement of surfaces. We will get acquainted with each of them in more detail.

Geometric leveling

With this method, terrain measurements use a special geometric rail and a level meter. The principle of shooting is to install the slats with strokes and divisions at the necessary point near the surface being studied. Then, using a horizontal sight beam, the altitude difference is measured. Geometric leveling is performed on a "from the middle" or "forward" principle. When measuring the first method in two points of the surface set the slats, the device is located between them at an equidistant distance. The result of shooting is the data on the excess of one of the bars over the other. The second method is classic - one device and one rack. These methods of leveling are the most common. They are used in the construction of both small objects (houses) and large (bridges).

Trigonometric leveling

With this type of measurement work, it is customary to use special goniometric devices called theodolites. With the help of them, information is extracted about the angles of inclination of the beam of the visor, which passes through a pair of given points on the surface. Trigonometric leveling is widely used in topographic measurements to determine the height difference between two objects that are at a considerable distance from each other, but in the optical visibility zone of the device.

Barometric measurement of the surface

Barometric leveling is a measurement method based on the dependence of atmospheric air pressure on the height of the point of the surface being determined. The reading process is performed using a barometer. This leveling system must take into account a number of corrections to the actual air temperature, to its humidity. This method was used in hard-to-reach areas (for example, in mountainous conditions) under various geographic and geological expeditions.

Mechanical (technical) measurement of the surface

Technical leveling involves the use of a special device - leveling automaton. With the help of it, the profile of the studied terrain is automatically plotted using a friction disk that records the distance traveled, and the installed plumb bob that defines the vertical. Such a device is usually installed on a vehicle and travels from one designated point to another. Technical leveling allows you to determine the height difference between the studied objects, the distance between them and the terrain profile, which is fixed on a special photographic tape.

Hydrostatic surface measurement

Hydrostatic leveling is a method based on the principle of the action of communicating vessels. Shooting this way is done with a hydrostatic device that works with an error of up to two millimeters. This level is made up of a pair of glass tubes connected by a hose, this system is filled with water. The measurement process is carried out as follows: the tubes are attached to the slats on which the scale is applied. After that, the bars are placed near the objects under study, by dividing the numerical value of the difference between the two levels. This design has a significant drawback, namely the limited measurement limit, which is determined by the length of the hose.

The described methods of leveling (except for mechanical ones) are very simple and do not require the presence of specific knowledge baggage from the operator, therefore they are widely used in construction and other spheres of the national economy.

Measurement classes

In addition to the measurement procedure, leveling is usually divided into accuracy classes. Each of them corresponds to a certain type and method of implementing information retrieval. Consider what are the grading classes.

1. The first class is considered high-precision. It corresponds to a mean-square random error equal to 0.8 millimeters per kilometer and a systematic error of 0.08 mm / km.
2. The second class is also considered high-precision. However, the error here is somewhat higher - the rms error is 2.0 mm / km, and the systematic error is 0.2 mm / km.
3. Third class. It corresponds to a root-mean-square error of 5.0 mm / km, and a systematic error is not taken into account.
4. The fourth class. It corresponds to a root-mean-square error of 10.0 mm / km, the system error is also not taken into account.

Depending on the characteristics of the terrain and the tasks of shooting, various methods of shooting data can be used. For example, in polygons, along parallel lines or surface leveling by squares. The latter method is most widely used, it is widely used for data collection from large open areas with a relatively small section height. Let's consider it in more detail.

Breakdown by squares

Surface leveling by this method is carried out with the aim of obtaining topographic large-scale plans of flat areas. Smooth position of the control points is determined by laying the theodolite moves. A height - a method of geometric measurement using technical levels. The process of data extraction can be carried out in two different ways: by laying level moves with a gradual breakdown of the widths and by squares.

Leveling by squares is performed by breaking down on the terrain using a measuring tape and a theodolite (grid with a side of the cell of twenty meters) when measured on a scale of 1: 500 and 1: 1000, forty meters - when shooting at a scale of 1: 2000 and one hundred meters at 1: 5000.

At the same time, the situation of the studied territory is fixed and an outline is drawn up. This procedure is performed in the same way as in theodolite survey. In addition to the tops of the cells, characteristic features of the terrain are fixed in the terrain - plus points: the top and bottom of the hill, the bottom and edges of the pit, the points on the weirs and watershed lines, and others.

Shooting justification is created by laying on the outer boundaries of a grid of squares of leveling and theodolite moves, which then are attached to the points of a single state network. The heights of the plus points and the vertices of the cells are determined by the method of geometric leveling. If the length of the side of the square is forty meters or less, then from one station they try to measure all the points to be determined. The distance from the device to the bar should not exceed 100-150 meters. If the length of the side of the square is one hundred meters, then the level is placed in the center of each cell. According to the data of the field survey of the area, the method of squares consists of a log of leveling and the outline of measurements.

Journal and outline of leveling by squares

The log is entered data on the size of the side of the cell, the binding of the grid to the theodolite moves (geodetic justification). In addition, the reference to the terrain objects - lakes, hills and so on - is indicated. Also it should be noted from what positions the leveling of the terrain was made. The results of shooting each of the squares are recorded in the outline. The vertex and the plus point of each cell indicate the readings from the black side of the bar (in meters), as well as the calculated heights. This calculation is performed on the horizon of the instrument. The heights of the vertices of the cells are determined as the difference in the tool horizon at the station and the count on the rail.

In order to control the process of measuring the surface, two levels of cells are leveled from two different stations. Drawing up a plan for the data obtained from the surface data collection begins with a fixation on the tablet on the coordinates of the points of the single state geodetic network, the objects of the survey justification (level-theodolite moves), plus points, the vertices of the squares and the situation.

Application Method

When leveling the territory by applying theodolite and leveling moves with a breakdown into diameters, the traces are plotted along the natural characteristic lines of the given terrain, for example, over weirs or watersheds. In such operations, the widths and pickets should be broken down every forty meters when shooting at a scale of 1: 2000 and after twenty meters when shooting at a scale of 1: 1000 and 1: 500. In the points of skate bends, plus objects are noted. In the process of breaking up pickets, it is necessary to fix the situation and draw up an outline. Records of leveling are produced in the journal. It marks the ordinal numbers of pickets, counts along the red and black side of the rails, the distances of plus objects from the nearest pickets. Based on the results of leveling, a topographic plan of the territory, cross and longitudinal profiles of the terrain are compiled.

Measurement of the surface is advisable to conduct on the sites of the proposed site of works on improvement and vertical planning of the territory. As an example, we can cite the landscape design of a terrain surrounding an architectural monument, or a garden and park zone.

What is a level?

To carry out a geometric measurement of the terrain, which is widely used in construction, the levels of various structures are used. These devices, according to their principle of operation, are usually divided into: electronic, laser, hydrostatic and optical-mechanical. All levels are equipped with a telescope rotating in the horizontal plane. The modern design of such a measuring instrument provides for automatic compensation for setting the visual axis in working position.

History of leveling

The first information that reached the modern man about the leveling, refer to the first century BC, namely the erection of irrigation canals in Ancient Greece and Rome. In historical documents, a water meter is mentioned. His invention and use are associated with the names of the ancient Greek scholar Heron of Alexandria and the Roman architect Mark Vitruvius. The impetus for the development of these measuring instruments and methods of leveling was the creation of a telescope, a barometer, a cylindrical level and a grid of grading in the telescope. These inventions date back to the 16th and 17th centuries, they allowed the development of a system for accurate land surface survey.

In Russia, during the time of Peter the Great, an optical workshop was founded, where, among other things, levels were produced, only then they were called levels with a pipe. The development of levels in the workshop was handled by IE Belyaev. In the same period, the first measuring instruments appeared, based on barometers. In the early nineteenth century, the first trigonometric levels appeared, with their help a very large-scale work was carried out to determine the difference in the levels of the Azov and Black Seas, and the height of Mount Elbrus was measured. The use of geometric devices was recorded in the middle of the nineteenth century. So, in 1847 they were used in the construction of the Suez Canal. In our country, the geometrical leveling of the surface was used in the construction of waterways and land roads. The beginning of the creation of the national state network is 1871. Then began work on fixing and installing the items that served as the basis for topographic surveying.

Application leveling

The result of leveling is the creation of a single reference geodetic network, which serves as the basis for conducting topographic measurements of the terrain or for various geodetic measurements. Shooting is widely used for research and scientific purposes: in the study of the globe, the motion of the earth's crust, to fix the fluctuations in the sea level and the oceans.

Leveling is also used to solve various applied problems, which are associated with the construction of various objects, the laying of communication lines, engineering communications, etc. For example, the measurement of the terrain is necessary for carrying out the transfer of design decisions in height, in addition, during installation work on the installation of building structures . When solving similar problems, the data received by the geodesy service is always used. Also, directly to solve various highly specialized tasks, automatic information retrieval systems are used. Such tasks include, for example, repair and construction of the roadway. Sensors included in the automatic leveling device are installed on railway cars and cars, resulting in a ready-made profile of the studied area in the shortest possible time.

Modern technologies

To date, due to the unusually rapid development of science and technology, various technical know-how is used to level the surface.

1. Laser. At the heart of their work is the reading of terrain parameters with the help of a laser scanning device.
2. Ultrasound. The main element of such a device is the ultrasonic wave emitting wave .
3. GNSS technology, which is associated with obtaining information about the current coordinates via satellite communication. Such equipment provides very high leveling accuracy.

To ensure efficient processing of a large number of information flows obtained by applying the above know-how, it is necessary to have appropriate special software that will perform tasks related to storage, management, visualization and data processing.

Modern leveling systems in road construction

Automated systems are widely used in modern road construction. They allow you to control road construction equipment, given its current position. At the same time, the automatic leveling of the track is characterized by high precision of the work carried out, which significantly improves the quality of the roadway produced, and also shortens the construction time. Such instruments installed on asphalt pavers, road cutters, bulldozers, allow to eliminate damages and defects of the old coating when laying a new layer. These levels control the transverse slope of the road, perform it according to the parameters specified by the project. Modern surface measurement systems for road construction equipment are divided into several types depending on the technology used.

1. Ultrasonic devices with different number of sensors.
2. Laser pick-up systems.
3. The device is based on satellite GPS-technologies.
4. A three-dimensional system that operates on the principle of a total station.

If necessary, depending on the complexity and specificity of the work being carried out, this or that automatic leveling technology can be used.