Control survey detailed data collection

Control survey refers to measuring the plane position and elevation of a series of control points in the survey area according to the accuracy required by the survey task, and establishing a survey control network as the basis for various surveys.

Control network has the function of controlling the overall situation and limiting the accumulation of measurement errors, and is the basis of all measurement work. For topographic mapping, slope control is the basis of extended root control to ensure that the measured topographic map can be spliced into a whole. For engineering survey, it is often necessary to establish a special control network as the basis for construction lofting and deformation observation.

Chinese name: control survey mbth: control survey establishment method: triangulation and traverse survey function: control the whole situation and limit the accumulation of measurement errors. Control survey and its tasks, characteristics, establishment methods, triangulation, traverse survey, trilateration, corner survey, small triangulation, regional control network, elevation control network, leveling survey, trigonometric leveling, adjustment calculation, control survey and its tasks are in the engineering construction area. The plane position and elevation of a series of control points are measured with necessary accuracy, and the engineering control network is established as the basis for topographic survey and engineering survey. This measurement is called control measurement. Engineering control network is divided into two parts: plane control network and elevation control network. The former is the plane rectangular coordinate of the survey control point, and the latter is the elevation of the survey control point. The specific tasks of control survey in the three stages of engineering construction are: establishing surveying and mapping control network in the survey and design stage as the basis of various large-scale mapping; Establish a construction control network in the construction stage as the basis for construction lofting measurement; In the operation stage, the deformation observation control network is established as the basis for deformation observation of engineering buildings. The control function of control survey on surveying and mapping topographic map is as follows: topographic map is divided into frames, and all topographic maps must be spliced into a whole, without loopholes, overlaps and distortions, and with the same accuracy. If a unified plane control network is established in the engineering construction area, and the Gaussian plane rectangular coordinates of each control point in the network are accurately measured, the position of each map sheet can be accurately found in the field, so that there will be no loopholes, overlaps and distortions between adjacent maps during independent mapping. Because of the high accuracy of the control points, the measurement error of the plane position of each topographic map will be limited by the control points and will not accumulate very much, thus ensuring that the plane position of each map has the same surveying and mapping accuracy. Therefore, the plane positions of two adjacent topographic maps can be connected with each other within the accuracy of surveying and mapping. Similarly, if a unified elevation control network is established in the engineering construction area and the elevation of each control point in the network is accurately measured, the contour lines of adjacent sheets can be connected with each other within the range of mapping accuracy when independently mapping. According to the characteristics of a certain area, a control network survey is established for geodesy, photogrammetry, topographic survey and engineering survey. Comprise that following step: ① plane control measurement, namely measuring the plane coordinates of control points; (2) elevation control survey, which is used to measure the elevation of control points; (3) Three-dimensional control survey, which is used to simultaneously measure the plane coordinates and elevation or three-dimensional coordinates of control points. The survey work carried out by establishing a control network (regional control network) in a certain area for topographic mapping or engineering survey. Divided into plane control survey and elevation control survey. Generally, the plane control network and the elevation control network are arranged separately, or a solid control network can be arranged. The datum plane of control survey is the geoid, and the plumb line perpendicular to the geoid is the datum line of the field. Geoid: Because the ocean accounts for 765,438+0% of the global area, it is assumed to coincide with the average sea level and extend to the horizon perpendicular to the vertical line under the mainland without being affected by tides, wind waves and pressure changes. It is called geoid, and it is a continuous closed surface without folds and edges. The establishment method is often used in triangulation, traverse survey, trilateration and corner survey. Triangulation is one of the basic methods to establish plane control network. However, triangulation (locking) requires each point to be visible to more adjacent points, and it is often necessary to establish higher beacons in hidden areas. Traverse survey traverse survey is simple, each point only needs to be interviewed with the front and back points, and it is convenient to select points, especially in hidden areas and cities with many buildings and difficult visibility, and the application is convenient and flexible. With the development of electromagnetic wave range finder, traverse survey has been widely used. Trilateral measurement Trilateral measurement needs to measure all the side lengths in the network. It can be solved by measuring the side length with electromagnetic wave distance meter. This method has few inspection conditions and low accuracy in calculating azimuth. The edge measurement method not only observes the angle of the control network, but also measures the edge length. Angle measurement is beneficial to control direction error, and edge measurement is beneficial to control length error. Corner * * * measurement can give full play to their advantages and improve the point accuracy. In engineering survey, it is not necessary to observe all angles and side lengths in the network, and some side lengths can be added on the basis of the angle measuring network or some angles can be added on the basis of the edge measuring network to achieve the required accuracy. Trigonometry trigonometry is a method of establishing a plane control network in a small survey area, which is mostly used for the first-level plane control in a small survey area or the encryption below the third and fourth triangulation networks, as a basis for expanding the root control network (points) directly used for topographic mapping. In addition, the intersection fixed point method is also a method to encrypt plane control points. Observing the horizontal angle of the fixed point at more than two known points and finding the plane position of the fixed point is called the forward intersection method; Observing the horizontal angles of more than three known points at the waiting point and finding the plane position of the waiting point is called the back intersection method. Compared with the national control network, the regional control network has smaller control area, higher control point density, smaller absolute error of points and higher accuracy. For the regional plane control network, according to the principles of survey area, development prospect, adjusting measures to local conditions, economy and rationality, and under the condition of ensuring the necessary accuracy and density of control points, it can be laid all at once or at different levels. Hierarchical network layout usually includes a large-scale first-level network, and then the encryption of low-level control points is carried out in stages. Graded cloth can adopt the same measurement method or different measurement methods. When designing, the accuracy should be estimated, and the mapping control network requires the accuracy of the whole network to be relatively uniform. The special control network for engineering survey sometimes needs to establish a high-precision local control network in a large control network. The regional control network is generally encrypted under the national control network, or a unified coordinate system with the national control network as the initial data. If there are no known control points available in the survey area, the latitude and longitude of any point in the network can be observed by astronomical method and converted into Gaussian -Kr rectangular coordinates as the starting coordinates. It is also necessary to observe the astronomical azimuth from this point to another point and convert it into the coordinate azimuth as the initial azimuth. In some cases, the assumed coordinates and magnetic north direction can also be used for small survey areas. The initial side length of triangulation can be measured directly by rangefinder. When the survey area is small, it can be regarded as a plane. However, in a larger area, the influence of the curvature of the earth should be considered. In order to deal with the length projection deformation reasonably, the projection belt and projection plane should be selected appropriately. Generally, the observation results should be normalized to the reference ellipsoid (or geoid), and the plane rectangular coordinates in the three zones should be calculated by Gaussian conformal projection, which should be consistent with the national coordinate system as far as possible, which is conducive to the mutual utilization of the results and maps. When the average elevation of the survey area is large, in order to make the results consistent with the field, the average elevation plane of the survey area should be used as the projection plane. When the midpoint of the survey area is far away from three central meridians, the central meridian of the survey area should be taken as the central meridian, and any Gaussian conformal projection should be adopted (see Gaussian -Kr plane rectangular coordinate system). The special control network in engineering survey often has its special requirements in some aspects. On the premise of meeting this requirement, there are several different network layout schemes to choose from. With the development of computing tools, the theory of optimization method can be applied to determine the best design scheme. The elevation control network is mainly established by leveling and trigonometric leveling. Leveling The elevation control network established by leveling method is called leveling network. The grade and accuracy of regional leveling network are consistent with that of national leveling network. The elevation control network can be laid out in an all-round way or at different levels. Leveling at all levels can be used as the first level elevation control of the survey area. The main network is generally arranged as a ring network, and can be arranged as an attached line or a node network when encrypting. The elevation of the survey area should adopt the national unified height system. When it is difficult to carry out joint survey in a small survey area, the assumed elevation can also be used. Triangular leveling trigonometric leveling is to calculate the height difference according to the vertical angle and horizontal distance between two points, and its accuracy is lower than leveling. In areas where the terrain fluctuates greatly and direct leveling is difficult, the elevation of triangular points is often measured to provide elevation control for topographic mapping. Triangular leveling can be arranged in the form of single line, closed loop, node network or elevation network. Triangular elevation route is generally composed of sides with shorter side length and smaller height difference, starting and ending at the elevation points of leveling joint survey. In order to ensure the accuracy of triangular elevation network, there should be a certain number of known elevation points in the network, which are obtained by direct leveling or leveling joint survey. In order to eliminate the influence of earth curvature and atmospheric vertical refraction as much as possible, both sides should observe each other. When establishing plane control network and elevation control network in adjustment calculation, in order to check and improve accuracy, there are often a certain number of redundant observation values (see survey adjustment). According to the principle of least square method, the observed values are adjusted to eliminate the contradiction between the observed values, obtain the most reliable results and evaluate the accuracy of the measured results. For the control survey with low observation accuracy, the approximate method can be used for adjustment calculation.