Geodesic condensation networks. State geodetic condensation networks and geodetic survey justification Points of condensation networks 1 2 categories

Geodetic condensation networks are developed on the basis of the state geodetic network and serve to justify large-scale surveys, as well as to conduct engineering and geodetic work at construction sites of large industrial facilities.

Planned geodetic condensation networks are created in the form of triangulation (triangulation networks) and polygonometry of 1 and 2 categories.

Triangulation 1st category develops in the form of networks and chains of triangles with a side of 1-5 km, as well as by inserting individual points into the network upper class. Angles are measured with a mean square error of no more than 5", relative error output sides - no more than 1: 50,000.

Triangulation 2 digits is constructed in the same way as 1st category triangulation; in addition, the position of points of the 2nd category can be determined by forward, backward and combined geodetic intersections. The lengths of the sides of triangles in 2nd-bit networks are taken from 0.5 to 3 km, the mean square error in measuring angles is -10", the relative error of the output sides is no more than 1:20,000.

Polygonometry 1st and 2nd grades is created in the form of single passages or systems with nodal points, the lengths of the sides of which are taken on average equal to 0.3 and 0.2 km, respectively. The mean square error of measuring angles in polygonometry moves of the 1st category is 5", the relative error of measuring lengths is 1:10,000.

In 2nd grade polygonometry, the accuracy of angular and linear measurements is 2 times lower compared to 1st grade polygonometry.

All points of geodetic condensation networks must be marked by class IV leveling or technical leveling. In mountainous areas, it is allowed to transfer point marks by trigonometric leveling.

Survey justification develops from points of state geodetic networks and geodetic condensation networks. Survey networks are created by constructing survey triangulation networks, laying out theodolite, tacheometric and scale traverses, forward, backward and combined intersections. When developing a survey justification, as a rule, the plan and elevation positions of the points are simultaneously determined. The heights of survey network points are determined by trigonometric or geometric leveling.

1:1000

1:2000

1:5000

Shooting scale

Number of points per 1 sq. km

GEODETIC CONDENSATION NETWORKS AND SURVEYING NETWORKS

Survey geodetic networks (geodetic survey

justification) are created to thicken the geodetic network to a density that ensures topographic surveying.

The density of survey networks is determined by the scale of survey, the nature of the terrain, as well as the need to provide geodetic, surveying and other work for the purposes of survey, construction and operation of structures.

A theodolite traverse is a system of points fixed on the ground, the coordinates of which are determined from measurements of horizontal angles and lengths of the sides of the traverse. According to the form and completeness of the initial data, linear-angular moves are divided into the following types:

open stroke - starting points with known coordinates and initial directional angles are at the beginning and end of the stroke;

closed theodolite traverse - the starting and ending points of the move are combined; one point of the move has known coordinates and is called the starting point; at this point there must be an initial direction with a known directional angle, and the adjacent angle between this direction and the direction to the second point of the move is measured.

free traverse has no starting points and starting directional angles either at the beginning or at the end of the stroke; a hanging linear-angular passage has a starting point with known coordinates and a starting point directional angle only at the beginning of the turn.

The lengths of the sides between the points of theodolite passages range from 20 to 350 m. The maximum permissible stroke length depends on the shooting scale.

The rotation angles at the traverse points are measured with a theodolite with a mean square error of 0.5′ in one step. The discrepancy between the angle values ​​in half moves is allowed no more than 0.8′. The length of the lines in the passages is measured with light range finders or tape measures. Each side is measured twice - in the forward and reverse directions. Discrepancies in measured values ​​are allowed within 1:2000 of the measured line length.

Points of geodetic networks are fixed on the ground by underground centers, which must ensure the unchanged position and safety of the point for a long time.

The types of underground centers are established depending on the physical and geographical conditions of the region, the composition of the soil and the depth of seasonal freezing of the soil. For example, the center of a point of the state geodetic network of classes 1-4 of type 1 consists of a reinforced concrete pylon with a section of 16X 16 cm (or an asbestos-cement pipe 14-16 cm filled with concrete) and a concrete anchor. Pylon

cemented into the anchor.

The base of the center must be located below the depth of seasonal soil freezing of at least 0.5 m and at least 1.3 m from the surface of the earth. In the upper part of the sign, at the level of the ground surface, a cast-iron mark is concreted indicating the point to which the coordinates of the point relate. An identification pole with a security plate is installed 1 - 1.5 m from the center.

FIXING AND MARKING POINTS OF THE GEODETIC NETWORK ON THE TERRITORY

Points of the high-altitude geodetic network are fixed ground benchmarks, wall benchmarks and marks. The ground benchmark in the upper part has a cast iron mark; the benchmark mark refers to the top point of the hemispherical protrusion of the mark.

The height of the wall benchmark is determined for the upper edge of the protrusion, and the height of the marks is determined for the center of the hole made in the disk. As external design The wall reference is a security plate cast from cast iron. It is fixed in the wall of a building or structure next to or above the wall benchmark.

Most of the survey network points are secured with temporary signs, which are wooden stakes or metal tubes at least 40-50 cm long, which are driven flush with the surface of the ground; the center of the wooden temporary sign is a nail driven into the upper end of the stake. To make it easier to find such a sign, a guard 30 cm high is hammered next to it.

They serve to continue covering regional territories with geodetic reference justification. The need to increase the density of geodetic points is dictated by common sense and ease of work for all participants in industrial relations. When all objects on the ground are oriented in a single coordinate system, it is comfortable for everyone to work with it: architects, designers, land managers, surveyors. The basis for solving many regional issues is, of course, large-scale topographic plans. And in turn, the basis for large-scale topographic surveys are geodetic condensation networks.

The points of state networks of the highest classes (from I to IV) are taken as the starting points when performing network thickening. It is known that the distances between them range from a maximum of thirty kilometers (for class I) to a minimum of five kilometers (for class III). The density of high-class networks is approximately one point per area on average 20-30 square kilometers when surveying at a scale of 1:5000. And when performing topographic surveys on a scale of 1:2000 and larger, the average density reaches 5-15 square kilometers.

Obviously, there is a need to further increase the number of geodetic points to cover the area with a reference survey justification. This is especially true for industrial and urban areas. An enlargement of the geodetic justification is required. Bring their density to four triangulation or polygonometry points per square kilometer in cities, towns, that is, built-up areas. It is also necessary to have at least one point per square kilometer in undeveloped areas of the area.

We know that the condensation of geodetic justification is carried out using the basic geodetic principle, namely: from the general to the specific. Thus, from the base highest quality(I, II, III, IV classes) networks of lower classes, or rather 1 and 2 categories, are built. Moreover, in order to reduce the stepwise nature of the development of geodetic constructions, it is necessary to use modern electronic measuring technology to construct networks of identical (single-digit) accuracy.

Construction and types of points of condensation networks of 1st and 2nd categories

To carry out basic geodetic work, technical projects are initially developed. They determine the optimal locations for points on topoplans of smaller scales (1:25000, 1:10000). In the process of carrying out reconnaissance already on the ground, they come to the final version of the laying sites, types of centers and the choice of external signs.

Points of condensation networks of 1st and 2nd categories have their own requirements depending on the method used in the technical project.

When triangulating, the bookmark distance between points should be within five hundred meters - five kilometers (1st category) and two hundred and fifty meters - three kilometers (2nd category). When using polygonometric moves provided for in the project, the lengths of the polygons must be within acceptable limits. And between individual, source and node points, the maximum distances vary from two to three and five kilometers for category 1, and from one and a half to two and three kilometers, respectively, for category 2 of the condensation network. Triangulation and polygonometric networks of the same category are equivalent in accuracy. Therefore, any of the methods that are more acceptable for the initial area with minimal economic costs will be a priority when choosing to carry out a set of works to thicken networks.

Each geodetic point of 1st and 2nd category is fixed in the ground by the center and, in accordance with the established guidelines for the construction of these signs, with the corresponding structures of external signals.

The main types of center designs are:

• tours;
• metal triangular pyramids;
• tripod pyramids;
• tetrahedral pyramids;
• complex signals (if necessary).

With geodetic tours, points can be fixed both on the ground in the ground and on building structures. In urban environments, they are constructed on the tops of buildings, rigidly connected to the structural elements of roofs or ceilings. Images of the tours are shown below in Fig. 1 and Fig. 2.

Fig.1. Tour with removable sighting target.

Fig.2. Tour with removable sighting target and measurement platform.

In areas with undeveloped territory, open areas, external signs are triangular or tetrahedral pyramids. They are made from metal corners, mainly with a cross section of 50×50×5 mm. At the top of the pyramids, sighting targets are constructed, which are made of a pipe 500 mm long and with a circular cross-section with a radius of 250 mm. An image of ground signs in the form of pyramids is shown in Fig. 3.

Fig.3. External signs: triangular and tetrahedral pyramids.

In addition to standard ground signs, there are also special devices called tripod pyramids. Some of them have retractable sighting targets up to 19 meters high, mounted on guy wires. Sighting targets are placed on retractable ties using a mechanized method only for the duration of observations. The height of the target itself should not exceed two values ​​of the height of the pyramid. An image of the outer sign of the tripod pyramid is shown in Fig. 4.

Fig.4. Pyramid tripod with a table and a retractable sighting target.

All ground signs have rigid structures with stable bases and durable elements. As a rule, they are always treated with an anti-corrosion coating.

The centers of points of condensation networks are different types depending on the location, geographic area, soil characteristics, and climatic conditions. Typical centers provide for fixing centers in sandy soils, hard surfaces and soils with seasonal freezing. Images of such centers are shown in Fig. 5, 6, 7.

Fig.5. Hard surface center.

Fig.6. Center for shifting sands.

Fig.7. Center for soils with seasonal freezing.

When constructing geodetic centers within the city, it is necessary to secure them with special marks with central holes in tours installed on top of buildings. In addition, they can be fixed in the upper ceilings, on metal structures such as water intake grates. The resulting holes with a diameter of up to two to four mm and a depth of up to five mm are stamped with non-ferrous metal, such as copper, and correspond to the center with the bearing actual coordinates. Among other things, sometimes the design of the centers of geodetic points of discharge networks is carried out nearby with reinforced concrete pillars installed in the ground with security platinum. This always happens in the absence of permanent external signs on them. An image with a diagram of the construction of a geodetic point is shown in Fig. 8.

Fig.8. Scheme of a geodetic point with an identification pole.

To increase the density of points of the reference geodetic network, geodetic condensation networks are built. Condensation networks are classified according to categories. Triangulation and polygonometry networks of classes 1 and 2 are developing relative to points of the state geodetic network of classes 1–4. The base sides in triangulation networks of 1st and 2nd digits are measured by light rangefinders, and the angles are measured by precise T2 theodolites using circular techniques. The length of the side of the triangle in the 1st category condensation network should not exceed 5 km, 2nd category - 3 km. The maximum error in angle measurements is no more than 5 seconds. The relative error of the base side for networks of 1st category is 1:50,000, 2nd category - 1:20,000. Polygonometric condensation networks created in the form of separate passages have side lengths from 0.12 to 0.8 km with a length measurement error of 1: 10 000. The average error in measuring angles is no more than 5 seconds. In 2nd-bit condensation networks, the side length ranges from 0.08 to 0.35 km with an error of 1:5000. High-altitude thickening networks are created using the IV class leveling method or technical leveling. Discrepancies in traverses and polygons should not exceed 50 L, mm, where L is the traverse length, km. In accordance with the instructions for topographic survey, the number of points of the state geodetic condensation network in cities should be 4 points per 1 km 2 in built-up areas and up to 1 point per 1 km 2 in undeveloped areas. During engineering surveys, the density of the geodetic network can reach up to 8 points per 1 km 2. The surveying geodetic network, necessary for performing engineering and geodetic work in construction, is created by constructing triangulation networks and polygons using tacheometers and scales with forward and backward combined serifs. The heights of survey justification points are determined by technical or trigonometric leveling.

Fixing points of geodetic networks. To ensure the unchanged position of points of the planned state geodetic network for a long time, they must be fixed on the ground. Depending on the composition of the soil and the depth of soil freezing, special centers with a depth of about 2 m are created for shallow freezing of the soil. The center of the geodetic mark is located in the well, above which an identification column is installed. To ensure mutual visibility between points, pyramids of various designs are installed above the centers of geodetic signs. IN

Center of geodetic symbol

Geodetic signs:

a- pyramid; b - signal

A sighting cylinder is installed on the top of the pyramids to provide angular measurements. Depending on the terrain conditions, geodetic signs may have different designs. In open areas with good visibility between points, angular measurements are made from a tripod installed on the ground directly above the center of the geodetic network point. In forest conditions, signals up to 40 meters high are built on the ground. In this case, the device for measuring angles is installed on a special table located in the upper part of the signal. In this case, it is necessary to comply with the condition that the center of the table, the center of the geodetic point and the axis of the sighting cylinder must be on the same plumb line. In cities with multi-story buildings, triangulation points are installed on the roofs of high-rise buildings. This point is a brick or concrete pillar with a sighting cylinder. The column is used to place a goniometer on it. Points of the high-altitude state geodetic network are special signs, namely: wall benchmarks, marks or ground benchmarks. Wall benchmarks and marks are fixed in the walls of fundamental buildings. The mark mark corresponds to the center of the hole in the mark disk into which the leveling rod is suspended. The wall benchmark mark corresponds to the shelf on which the batten is installed. The main altitude symbol of the geodetic state network is the wall benchmark. If there are no fundamental buildings near the point of the geodetic support network, then to secure it, a ground reference is laid, consisting of a steel pipe or a piece of rail. These metal parts are embedded in concrete monoliths. A mark with a spherical head is placed on top of the steel pipe. When leveling, the top part of the head is taken as the starting point. Points of surveying geodetic networks are fixed on the ground with temporary signs: wooden posts, pegs, sections of metal pipes, etc. The coordinates of all points of the planned geodetic network, as well as marks of points of the high-altitude geodetic network, are entered into special catalogs, in which, in addition to the names of the points, a description of their location is given.

Geodetic network call a set of points on the earth's surface, fixed by special centers, the position of which is determined in a common system of coordinates and heights.

There are planned, high-rise and spatial networks. Planned networks– these are those in which plan coordinates are defined (flat - x, y or geodetic - latitude B and longitude L) points. IN high-altitude networks determine the heights of points relative to a reference surface, for example, the surface of a geoid (or rather, a quasi-geoid). IN spatial networks determine the spatial coordinates of points, for example, rectangular geocentric X, Y, Z or geodetic B, L, H.

Geodetic networks are classified according to their purpose into state geodetic networks, thickening geodetic networks, special-purpose geodetic networks and survey networks.

State geodetic network. The state geodetic network covers the entire territory Russian Federation and serves as its main geodetic basis. The State Geodetic Network (GNS) is designed to solve the following main tasks of economic, scientific and defense significance: establishing and disseminating a unified coordinate system throughout the country and maintaining it at the level of modern and future requirements; geodetic support for mapping the territory of the country and the waters of the surrounding seas; geodetic support for the study of land resources and land use, cadastre, construction, exploration and development of natural resources; provision of geodetic data to means of land, sea and aerospace navigation, aerospace monitoring of the natural and man-made environment; study of the surface and gravitational field of the Earth and their changes over time; study of geodynamic phenomena; metrological support of high-precision technical means location and orientation determination.

As measuring instruments are improved and new data are accumulated, the GGS is being modernized and now includes: a fundamental astronomical-geodetic network, a high-precision geodetic network, a class 1 satellite geodetic network, as well as an astronomical-geodetic network and geodetic condensation networks.

Condensation networks. Where further network densification is required (for example, in populated areas), relying on the state geodetic network, they develop condensation networks 1 and 2 categories, which achieves a density per 1 km 2 of at least 4 points in a built-up area and 1 point in an undeveloped area.

Filming network created when surveying the area. It develops from points of the state geodetic network and condensation networks of 1 and 2 categories. But when shooting individual areas, the survey network can be independent, built in a local coordinate system. In survey networks, as a rule, the position of points in plan and height is simultaneously determined.

The maximum errors in the planned position of survey network points relative to the starting points should not exceed 0.2 mm on the plan scale in open areas and built-up areas and 0.3 mm in areas covered by trees and shrubs.

The coordinates of survey network points are determined by laying theodolite traverses, constructing triangulation, serifs, the satellite method, etc. Theodolite traverses are the most common.

Points of geodetic networks are fixed on the ground special signs- centers designed to ensure the sustainability and long-term preservation of points.

The type of center depends on the purpose of the network and the nature of the soil. Official regulatory documents Standard designs of centers have been established, depending on the class of the point and local conditions. They are different for areas of seasonal soil freezing, for areas of permafrost, and for areas of moving sand.

Ticket No. 17 and No. 18. Methods for constructing a planned (horizontal) geodetic network: triangulation, polygonometry (18), trilateration.

When constructing planned networks, individual points of the network serve as initial points - their coordinates must be known. The coordinates of the remaining points are determined using measurements connecting them with the original ones. Planned geodetic networks are created using the following methods.

Triangulation – a method of determining the planned position of geodetic points by constructing a network of triangles on the ground in which angles are measured, as well as the lengths of some sides, called base sides (Fig. 5.1).

Let us assume that in the triangle ABP the coordinates of the points are known A( , ) And B( , ). This allows, by solving the inverse geodetic problem, to determine the length of the side and the directional angle of direction from the point A per point B. Lengths of the other two sides of the triangle ABP can be calculated using the sine theorem; .

Continuing in this manner, the lengths of all sides of the network are calculated. If, in addition to the basis b other bases are known (in Fig. 5.1 the bases are shown by a double line), then the lengths of the sides of the network can be calculated with control.

Directional angles of the sides AP And BP triangle ABP equal ; .

Point coordinates P will be determined by the formulas of the direct geodetic problem; .

The coordinates of all other points are calculated similarly.

Trilateration – a method of determining the planned position of geodetic points by constructing a network of triangles on the ground, in which the lengths of their sides are measured.

If in a triangle ABP(Fig. 5.1) the basis is known b and the sides and are measured, then based on the cosine theorem, the angles of the triangle can be calculated; ; ; . The angles of all triangles are also calculated, and then, as in triangulation, the coordinates of all points Polygonometry – a method of determining the planned position of geodetic points by laying a broken line (polygonometric traverse) or a system of interconnected broken lines (polygonometry network), in which the angles of rotation and lengths of the sides are measured.

Currently, the most effective method for creating a geodetic network, including geodetic condensation networks, is a method associated with satellite technologies(GL0NASS, GPS). However, this method requires receiving equipment, the high cost of which prevents its widespread use. Therefore, along with highly efficient satellite technologies, traditional methods are also used. It should be noted that when performing geodetic works in closed spaces and in cramped conditions, when observing a constellation of satellites is impossible or difficult, traditional methods are the only possible ones for solving many problems.

Geodetic condensation networks are built using triangulation and polygonometry methods to thicken the state geodetic network to the density necessary to create a survey justification for large-scale surveys. Triangulation of the 1st and 2nd categories is developed in open and mountainous areas. Where it is impossible or impractical to perform triangulation of the 1st and 2nd categories due to terrain conditions, a polygonometric network of the 4th class, 1st and 2nd categories is developed. It should be noted that class 4 polygonometry for large-scale surveys is performed with reduced accuracy compared to state surveys.

When creating polygonometry, they perform the entire complex of basic geodetic work: angular and linear measurements, leveling. Angles at polygonometry points are measured using the individual angle method or circular techniques using optical theodolites. T1, T2, T5 with a centering accuracy of 1 mm. Heights to all polygonometry points are transferred by class IV or technical leveling. Lines are measured directly: with light rangefinders, suspended measuring instruments, or indirectly - the lengths of the sides of the stroke are calculated using auxiliary quantities.

When carrying out various national economic, including land management, activities over a large territory, topographic maps and plans are required, drawn up on the basis of a network of geodetic points, the planned position of which on the earth's surface is determined in unified system coordinates, and the altitude - in a single height system. In this case, geodetic points can be only planned or only high-altitude, or simultaneously - planned and high-altitude.

A network of geodetic points is located on the ground according to the project drawn up for it. Network points are fixed on the ground with special signs.

A geodetic network built over a large area in a single system of coordinates and heights makes it possible to properly organize the work of surveying the area. If such a network is available, shooting can be carried out independently in different places, which will not cause difficulties when drawing up a general plan or map. In addition, the use of a network of geodetic points leads to a more uniform distribution of the influence of measurement errors over the territory and provides control over the geodetic work being carried out.

Geodetic networks are built according to the principle of transition from the general to the specific, i.e., first, over a large area, a sparse network of points is built with very high accuracy, and then this network is condensed sequentially in stages with points, the construction of which is carried out at each stage with less accuracy. There are several such stages of condensation. The condensation of the geodetic network is carried out in such a way that the result is a network of points of such density (density) and accuracy that these points can serve as direct support for the upcoming survey.

Planned geodetic networks are constructed mainly by the methods of triangulation, polygonometry and trilateration.

The triangulation method consists of constructing a network of triangles in which all angles of the triangles and at least two sides at different ends of the network are measured (the second side is measured to control the measurement of the first side and establish the quality of the entire network). Based on the length of one of the sides and the angles of the triangles, the sides of all Triangles of the network are determined. Knowing the directional angle of one of the sides of the network and the coordinates of one of the points, you can then calculate the coordinates of all points.

The polygonometry method consists of constructing a network of passages in which all angles and sides are measured. Polygonometric traverses differ from theodolite traverses in their higher accuracy of measuring angles and lines. This method is usually used in closed areas. The introduction of electromagnetic rangefinders into production makes it expedient to use polygonometry in open areas.

The trilateration method consists of constructing a network of triangles by measuring all sides of the triangles. In some cases, linear-angular networks are created, which are networks of triangles in which the sides and angles are measured (all or in the required combination).

Planned geodetic networks are divided into the state geodetic network; condensation networks of 1st and 2nd categories; shooting justification - filming network and individual points.