Explanation of Surveying Terminology 1 Surveying 2 Geodesy 3 Photogrammetry Problems: Methods of Plane Control and Elevation Control Surveying?

1. Early definition: study the shape and size of the earth and determine the coordinates of ground points.

2. Current definition: the study of the shape, size, position, direction and distribution of various objects in three-dimensional space.

The content of surveying includes two parts: measurement and layout. Measurement refers to the use of measuring instruments and tools to obtain a series of measurement data through measurement and calculation, or to draw the terrain of the earth's surface into a topographic map. Plane layout refers to marking the positions of planned buildings and structures on the drawings on the ground as the basis for construction.

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(2) Geodesy

Geodesy: the study of the measurement methods, distribution and application to determine the shape and size of the earth and its gravity field.

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(3) Photogrammetry

Photogrammetry: the study of the methods and theories of measurement using space, aviation and ground photography and remote sensing information.

Questions and answers:

Ground control survey is divided into two parts: plane control and elevation control.

(1) plane control survey

The main task of plane control survey in tunnel engineering is to determine the plane position of each hole control point, so as to guide the design direction under the ground according to the hole control points, guide the tunnel excavation, and carry out the penetration according to the specified accuracy. Therefore, the plane control network should include tunnel entrance control points. There are generally several methods for plane control measurement.

① Direct alignment method

For the straight tunnel with short length, the direct alignment method can be adopted. As shown in figure 12-3 1, point A and point 0 are the design entry points of the straight tunnel. The direct alignment method is to mark the centerline direction of the straight tunnel on the ground, that is, ignite the entrance in the 0-direction tunnel. When bow 1 is used to measure the centerline direction, two points, the moon and C, located in the straight direction of AD, are determined as the orientation points.

According to the general orientation, place the theodolite at 4 o'clock. Make it a month. Move the theodolite to point B' and extend the straight line to point C' with front and rear mirrors. Move the theodolite to the Cf point, and extend the straight line to the 0' point near the 0 point in the same way. While extending the straight line, determine the lengths of "Moon", "C" and "D" with theodolite sight distance method or rangefinder, and measure the length of D'0. Calculate the displacement of point C. Measure c "c along the direction perpendicular to CfD at CJ point, and determine point C. Put the theodolite at point C, extend DC to the moon point with front and rear mirrors, and then extend the subordinate point to point A. If it does not coincide with point A, make a second approach until the moon and point C are correctly located in the AD direction. Two points, Moon and C, can be used as directional points to indicate the heading direction at 0 o'clock, and the subsection distances of 4, Moon, C and 0 can be measured with a range finder, and the relative error of ranging should not be greater than 1: 5000.

② Traverse survey method

Connect two tunnels and lay one or two roughly parallel wires. The rotation angle of the conductor is observed by U2 theodolite, and the distance is measured by photoelectric rangefinder. The relative error is less than 1: 10000. Through the inverse calculation of the two-point coordinates of the hole, the distance and azimuth of the two-point connection direction can be obtained, and the course can be calculated accordingly.

③ Triangulation method

For mountainous areas with long tunnels and complex terrain, the ground plane control network is generally laid in the form of triangular network, as shown in figure 12-32. Determine all angles and several side lengths, or all side lengths of a triangular mesh to make it an angular mesh. The point accuracy of triangulation is higher than that of traverse, which is beneficial to control the transverse error of tunnel penetration.

④GPS method

When the global positioning system (GPS) technology is used for ground plane control, it is only necessary to arrange hole control points and orientation points and see each other, so as to achieve the purpose of construction orientation. Intervisibility is not required for points between different holes, nor for joint survey with national control points or urban control points. Therefore, the layout of ground control points is flexible and convenient, and the positioning accuracy is better than that of conventional control methods.

(2) elevation control survey

The task of elevation control survey is to measure the leveling point elevation near the tunnel entrance (including tunnel entrance, shaft entrance, inclined wellhead and quiet entrance) according to the specified accuracy, as the basis for entering the tunnel elevation survey. Elevation control usually adopts the method of third and fourth class leveling.

In leveling, the smoothest and shortest connection holes should be selected to meet the requirements of less stations, fast observation and high accuracy. There should be no less than two leveling points buried in each hole, and it is advisable to place a level for joint measurement. When the hole spacing at both ends is greater than 1km, temporary leveling points should be added in the middle.