What are the measuring instruments? Several control points are set up during the construction phase

If you use GPS to measure, the general practice does not care about how many levels of control points he is, the total length of 6 kilometers at both ends and about the middle position, the surrounding conditions are relatively good, there is no large area of water and occlusion of the position (to avoid the multipath effect) to do 3 control points can absolutely ensure that the horizontal accuracy is within 5cm, if you use a total station, 2 control points are enough, and you can calculate the closure difference yourself.

The purpose of control measurement is to confirm the plane position of the control point, and finally establish the plane control network, which is to establish a unified reference system for the next measurement work of the survey area.

Control measurement refers to the determination of the plane position and elevation of a series of control points in the survey area according to the accuracy required by the measurement task, and the establishment of a measurement control network as the basis for various measurements. The control network has the function of controlling the overall situation and limiting the accumulation of measurement errors, which is the basis for various measurement work.

Establish methods

Commonly used triangulation, traverse, trilateration and corner measurement are established.

Triangulation is one of the basic methods for establishing a plane control network. However, the triangulation network (lock) requires each point to be visible to more neighboring points, and it is often necessary to build a higher target in hidden areas.

The traverse measurement is simple to arrange, each point only needs to be visualized with the front and back two points, and the selection of points is convenient, especially in the hidden areas and cities where there are many buildings and it is difficult to see, and the application is convenient and flexible. With the development of electromagnetic wave rangefinders, the application of traverse measurement is becoming more and more extensive.

Trilateration requires the measurement of all the edge lengths in the net. The solution can be performed by measuring the edge length using an electromagnetic wave rangefinder. The verification conditions of this method are few, and the accuracy of calculating the azimuth angle is low.

The purpose of engineering control measurement is to limit the accumulation of measurement errors, which is the basis for various measurement work.

For topographic mapping, hierarchical control is the basis for extending the root control to ensure that the surveyed topographic maps can be stitched together into a whole.

For engineering surveying, it is often necessary to lay a special control network as the basis for construction lofting and deformation observation.

Features of construction engineering surveying:

1. High requirements for measurement accuracy.

In order to meet the requirements of higher construction measurement accuracy, the measuring instruments and tools that have been calibrated should be used for measurement operations, and the working procedures of measurement operations should conform to the general principle of "first the whole and then the part, first control and then the details", and the internal calculation and field measurement should be carefully operated, pay attention to the review, in case of errors, and the measurement methods and accuracy should meet the requirements of the relevant measurement specifications and construction specifications.

2. Measurement is closely related to construction progress.

At the construction site, each process often crosses operations, frequent transportation, and has a large number of earthwork filling and material stacking work, which affects the site conditions of the measurement operation, obstructs the line of sight, and destroys the measurement pile points.

Therefore, all kinds of measurement marks must be buried firmly, and located in a position that is not easy to be damaged and touched, in addition to frequent inspection, if damaged, should be restored in time to meet the needs of construction site measurement.

Prevents the accumulation of errors and improves measurement accuracy.

3. All construction control measurements include the coordinate system design and precision design of the construction control network, the laying of the construction control network, the burial or construction of the marker stone or observation pier of the control point, the observation and adjustment calculation of the control network, and the regular retest of the control network.

The construction control survey is the measurement of the construction control network, and the control range is small and the density of control points is large.

Construction control surveys are divided into plane control surveys and elevation control surveys.

The main task of measurement is measurement and measurement. Control measurements include plane control measurements and elevation control measurements. Therefore, in a nutshell, the basic task of control surveying is to determine and measure the plane position and elevation of the control point.

The construction work, which is the object of control and measurement services, can be roughly divided into three stages: design, construction, and operation. Each stage places different demands on the control measurement, and its basic tasks are described below:

1.In the design phase, a mapping control network for surveying and mapping large-scale topographic maps is established.

At this stage, the designer needs to design the building or plan the area on a large-scale topographic map to obtain the data on which the design is based. Therefore, the task of control survey is to lay out the mapping control network as the basis of root control, so as to ensure the accuracy of the topographic map and the accurate splicing between the topographic maps. In addition, for the real estate business, this mapping control network is also the basis for the corresponding cadastral survey.

2.Establish a construction control network during the construction phase.

At this stage, the main task of the construction survey is to stake out the building designed on the drawing board to the ground. The specific tasks of construction surveying are different for different projects. For example, the main task of tunnel construction survey is to ensure that the tunnel excavated in the opposite direction can be penetrated according to the specified accuracy, and the buildings are built according to the designed position; In the lofting process, the direction and distance marked by the instrument are calculated according to the control network and the buildings designed on the drawings.

Therefore, before the construction lofting, it is necessary to establish a construction control network with the necessary accuracy.

3.During the operation phase after the completion of the project, a dedicated control network for deformation observation will be established to monitor the deformation of the building.

Due to the change of the original state of the ground during the construction phase of the project, and the weight of the building itself, it will cause uneven changes in the foundation and the surrounding strata. In addition, the building itself and its foundation will also be deformed due to the change of the foundation, and this deformation, if it exceeds a certain limit, will affect the normal use of the building, and seriously endanger the safety of the building. In some large cities (such as Shanghai and Tianjin, China), due to the excessive exploitation of groundwater, it will also cause large-scale land subsidence in urban areas, thus causing harm.

Therefore, deformation monitoring of such suspected buildings or urban areas is required during the post-completion operation phase. To this end, it is necessary to lay out a deformation observation and control network. Since the values of such deformations are generally very small, in order to be able to measure them accurately enough, the deformation observation control network is required to have high accuracy.

Answer] :d 2022 Textbook p170 2021 2020 Textbook p166 page.

Before the start of the project, the measurement and control plan should be prepared and implemented after approval by the technical person in charge of the project. The survey control points provided by the relevant departments should be reviewed in the construction preparation stage, and the construction survey should be carried out after the approval of the fight, and the survey records should be kept. During the construction process, the measurement control points and lines should be properly protected, and unauthorized movement is not allowed.

During the construction process, the construction survey must be carefully carried out to review the ICBC, which is the technical work responsibility that the construction unit should perform, and the review results should be submitted to the supervision engineer for re-inspection and confirmation, before the construction of the subsequent related processes can be carried out.

Answer] Huai key: d

This question examines the approval of the measurement control and closure scheme. Before the start of the project, the measurement control plan should be prepared and implemented after approval by the technical person in charge of the project. The survey control points provided by the relevant departments should be reviewed in the stage of construction quasi-lead preparation, and the construction survey and pay-off should be carried out after approval, and the measurement records should be kept.