Topographic survey method

Topographic survey includes control survey and detail survey.

Control survey

① Control survey is to determine a certain number of plane and elevation control points, which is the basis of topographic mapping. The control measurement of flat mapping is usually divided into first-order control measurement and root control measurement. The first-level control is based on geodetic control points, and some control points with high precision and uniform distribution are determined in the whole survey area through triangulation or traverse survey. Root control survey is to encrypt the control points that meet the needs of mapping by using triangulation and intersection fixed-point method under the first-level control. The elevation of the control point of the map root is usually determined by trigonometric leveling or leveling.

detail survey

(2) Detail survey is the operation of surveying and mapping the terrain. Ground feature points and terrain feature points are collectively called breaking points. The plane position of the inflection point is usually determined by polar coordinate method, and the elevation of the inflection point is usually determined by sight distance measurement method. According to the different instruments used, there are flat mapping method, theodolite and small flat mapping method, theodolite (with portable exhibition tools) mapping method and so on. Their workflow is basically the same. Before surveying and mapping, fix the drawing paper or polyester film on the surveying and mapping board, draw a coordinate grid on the map, expand the outline points and all control points, and conduct surveying and mapping after checking and confirming. When surveying and mapping maps, the control points drawn on the surveying and mapping board or temporarily measured points are used as measuring stations, and leveling flat instruments are placed on the measuring stations and oriented. The edge of the ruler of the station is the direction line pointing to the breakpoint, and then the horizontal distance and elevation from the station to the breakpoint are measured by sight distance measurement. According to the measurement scale, the corresponding length, that is, the plane position of the breakpoint on the map, is intercepted along the edge of the ruler, and the elevation is marked next to the point. In this way, topographic maps can be mapped station by station.

Measurement method

According to the different instruments used, there are mainly flat plate mapping method, small plate mapping method combined with theodolite mapping method and theodolite mapping method in detail measurement.

Plane mapping method

Flat panel instrument consists of flat panel and alidade. The flat plate consists of a surveying and mapping plate, a base and a tripod; The collimator consists of a telescope, a vertical dial, a pillar and a ruler. Its function is similar to the sighting part of theodolite, but the difference is that the direction line is drawn along the ruler edge on the drawing board instead of the horizontal dial reading of theodolite. The tablet instrument also has some accessories, such as a counter for centering, a level meter and a long compass for orientation. When mapping, apply ι and B (Figure 2) corresponding to ground control points A and B that have been spread out on the mapping board, place a flat plate at point B, take B as the pole, point the flat plate in the direction of BA, then aim at the folding point C with a telescope, and the straight edge of point B is the direction line pointing to point C ... Then measure the horizontal distance from point B to point C and the elevation of point C by sight distance measurement, and intercept the corresponding length from point B along the edge of the ruler according to the mapping scale.

Theodolite mapping method

Place the theodolite on the control point, select a known direction as the zero direction, measure the horizontal included angle between the zero direction and the breakpoint direction, and measure the horizontal distance and elevation by the method of sight distance measurement. Put a drawing board next to the theodolite, use a protractor and a scale to determine the position of the breakpoint on the drawing board according to the polar coordinate method, and record the elevation. Measure and draw on the spot. If the observation data is brought back to indoor drawing, it is called theodolite recording method.

In the process of detail measurement, the density of control points can not fully meet the needs of measuring damaged parts, and a certain number of measuring stations need to be added to measure damaged parts.

Joint surveying and mapping method of small flat instrument and theodolite

The main difference between small flat-panel instruments and flat-panel instruments lies in the aiming equipment. The collimator of small flat-panel instrument consists of a ruler, a front plate and a rear plate, and a level is attached to the ruler. When mapping, put a small flat instrument on the control point to determine the direction from the control point to the breaking point. Place a theodolite next to it, measure the horizontal distance and elevation of the broken point by sight distance measurement, determine the position of the broken point on the map, write down the elevation, and draw while measuring. If it is in a flat area, a level can be used instead of a theodolite to measure the elevation of the broken point.

Topographic survey design

First, the main steps of topographic survey

1, work plan, and determine the implementation plan;

2. Collect the existing data of the survey area, and prepare the technical design of topographic survey according to the actual situation;

3. Organize personnel, set up a project department, set up a technical team and a quality inspection team;

4. Prepare all kinds of surveying and mapping instruments and equipment, and make surveying markers. ;

5. Control measurement;

6. Collect the field data of topographic map, including the plane position and elevation data of various ground objects and topographic points;

7, indoor computer data processing, drawing and all kinds of data processing;

8, quality inspection and acceptance work.

Second, the personnel and equipment configuration

In order to complete this topographic survey task on time with good quality and quantity, according to the requirements of workload, operation difficulty and operation time, the number of personnel and equipment to be invested is given in the following main stages:

1, control network selection and stone burying stage: 8 people are divided into 2 groups to select and bury the first-class traverse points.

2. Control network measurement stage: 8 people are divided into two groups, one group uses 4 GPS receivers to carry out first-class traverse GPS measurement.

3. Mapping root control survey and field data collection stage: 40 people are divided into 10 mapping group, and data are collected with 10 total station.

4. Data processing and graphic editing stage: A total of 65,438+00 computers are used, and the same graphic data processing and graphic editing software is used to process data and edit graphics according to the requirements of drawings, specifications, drawing specifications and design books.

5. Graphic output and on-site inspection stage: 40 people are divided into 10 groups to inspect the drawn paper map on the spot. At the same time, the terrain and object detection points are measured by total station. Deal with the problems found in time. At this stage, the project department will also organize self-inspection and re-inspection. After this stage, the whole field measurement stage ends.

6. Data processing stage: The data processing center employs 5 people and uses 5 computers to process the map data according to digital standards; The project manager and technical director will sort out and improve the control point notes, control point achievement table, technical summary, inspection report and other materials, conduct 100% inspection on the drawings, and finally submit the drawings, written materials and data discs.

From the beginning to the end of the whole project, the project manager and technical director should assume the responsibility of organization and leadership, strengthen technical guidance and quality supervision, often report the progress of the project to the competent leader, and adjust the personnel and equipment configuration in time according to the work progress and actual work progress to ensure the final project quality.