What Is Construction Surveying?

Construction survey refers to the measurement work of control, stake out and completion acceptance for construction. Contrary to the general mapping work, construction lofting is to mark the position, shape, size and elevation of the designed building on the ground according to the design drawings, so that construction can be carried out according to these calibrated points and lines. ^[1]

Construction survey is the survey work performed by various projects during the construction phase. Its main task is to measure (stake out) the plane position and elevation of the building designed on the drawing to the construction work surface with a certain accuracy according to the design and construction requirements during the construction phase, and use it as the basis for construction. During the process, a series of measurement and control work is performed to guide and ensure that the construction is carried out according to the design requirements.

Construction surveying directly serves the construction of the project, and it is both the leader of the construction and throughout the construction process. From site leveling, building (structure) building positioning, foundation construction, to wall construction, building (structure) building component installation and other processes, construction measurements are required to make the size of each part of the building (structure), Location meets design requirements. Its main contents are:

(1) establishment

There are various buildings and structures on the construction site, and the distribution area is wide, and they are often built in batches. In order to ensure that the planar position and elevation of buildings and structures can meet the design accuracy requirements, and they are interconnected to form a unified whole, construction surveys and topographic maps must follow the basic principles of surveying and mapping.

The basic principles of surveying and mapping work are: "from the whole to the local" in the overall layout; "control first and then broken steps" in the steps; and "from high to low" in accuracy. That is, a unified plane control network and an elevation control network are first established on the construction site. Then, based on the control network, the detailed positions of each building and structure were measured and set.

In addition, the calibration of construction surveys is also very important. If there is an error in the survey design, it will directly cause economic losses. In the process of setting and setting, the various setting and data and field testing and setting results should be checked in accordance with the principle of "checking and checking step by step. ^[3]

From the beginning to completion and completion of a civil engineering project, a number of surveys are required, mainly in the following three stages:

1. Survey work before construction starts

(1) The establishment of a construction site measurement control network;

(2) Land leveling and earthwork calculation of the site;

(3) Positioning of buildings and structures.

2. Survey work during construction

(1) Detailed positioning measurement and elevation measurement of buildings and structures;

(2) Axis survey of high-rise buildings;

(3) Installation and positioning measurement of structures and accessories;

(4) Deformation measurement of important buildings and structures during construction.

3 Survey work after completion

(1) Measurement and compilation of as-built drawings;

(2) Deformation measurement of subsequent important buildings and structures. ^[3]

1. High measurement accuracy

In order to meet the requirements of higher construction measurement accuracy, the calibrated measuring instruments and tools should be used for the measurement operation. The working procedure of the measurement operation should conform to the general principle of "first whole, then local, first control, then detailed". All field measurements should be performed carefully and checked to prevent errors. The measurement method and accuracy should meet the requirements of relevant measurement specifications and construction specifications.

For similar buildings and structures, when measuring the main axis of the entire building and structure in order to determine its positional relationship with other ground features, its measurement accuracy requirements can be relatively low. Associated axes, and when installing and setting out components, the accuracy requirements are relatively high; for deformation observation of buildings and structures, in order to find small changes in position and elevation, the measurement accuracy is higher.

2. Close relationship between measurement and construction progress

Construction measurement directly serves the construction of the project. Generally, stakeout measurement is performed before construction of each process. In order not to affect the normal progress of the construction, the corresponding measurement work should be completed in time according to the construction progress. Especially modern engineering projects are large in scale. The degree of mechanization is high, and the construction progress is fast, which puts forward higher requirements for close coordination of stakeout measurement.

At the construction site, the various procedures often cross operations, frequent transportation, and a large amount of earthfill excavation and material stacking work, affecting the site conditions of the survey operation, blocking the line of sight, and destroying the measuring pile. Therefore, various measurement signs must be buried firmly and placed in a location that is not easy to be damaged or touched. In addition, they should be checked frequently. If damaged, they should be restored in time to meet the needs of construction site measurement. ^[4]