Traditional Culture Encyclopedia - Photography major - Design and layout of target detection network
Design and layout of target detection network
The design of target detection network refers to the specific design of the following work contents of the survey network according to the geophysical exploration tasks and requirements (survey purpose, survey area address, survey area scope, work scale, survey network density, survey line orientation, survey network location and implementation survey specifications, etc.). ):
(1) Baseline number, orientation, passing position, inspection method, joint survey control point, joint survey method and baseline layout method;
(2) The number of survey lines, layout methods and verification methods;
(3) the number of measuring points;
(4) Instruments and equipment used;
(5) personnel organization;
(6) Submit materials, etc.
The design of target detection network should be carried out on the basis of full investigation.
(2) Layout of target detection network
The layout of the target detection network can be realized by the following scheme.
1. Network survey method
This is a method of laying a target detection network for all instruments. It is used for the layout of large object detection network, and theodolite is used for the direct layout of baseline and survey line. In recent years, it is faster and more accurate to set up a survey network with total station.
2. Method of controlling network
Used for the layout of target detection network with scale less than 1∶ 10000, which is divided into control line method and control point method. ① Control line method: survey the baseline and control line with instruments (the distance between control lines is generally 5 ~ 10 times of the distance between target detection points), and geophysical prospecting operators determine the target detection points with compasses and paces. ② Control point method: first set the baseline, and then set the survey line control point along the survey line direction from the base point. The distance between two points is generally 2 ~ 5 times of the distance between target detection points, and the layout of target detection points between corresponding survey line control points is the same as above.
3. Topographic map or orthographic image layout method
When used in the layout of small and medium-scale target detection network, the scale of topographic map or orthophoto image is larger than that of geophysical exploration. Firstly, the target detection network is drawn on topographic map or orthophoto map, and then the survey network is implemented by topographic map or orthophoto map.
4. Aerial photo cloth managed to
Try using a topographic map.
5.GPS cloth tries to
With the continuous development and popularization of GPSRTK technology, GPSRTK technology is now widely used to realize fast, efficient and accurate network layout.
(3) the layout of the baseline
When laying a baseline, first draw the baseline position, determine the starting point, then determine the baseline direction, then extend the direction line, and determine the baseline point according to the distance of the baseline point.
1. Proposed baseline position
The following conditions should be considered when the baseline position is drawn up: (1) plays a controlling role in the survey line; The baseline is close to the control point, so as to facilitate the survey or joint survey, and try to avoid areas with diverse features or complex terrain, so as to facilitate the survey. To draw up the baseline position, it is usually designed on the topographic map first. If the network is not fixed, the baseline design position can be slightly changed according to the site conditions.
Determine the starting point
The starting point can be any point on the baseline, which is generally selected on the map first, provided that it is convenient for layout or joint survey, and the point is safe and convenient for extending the baseline. The layout method of the starting point should be measured according to the method of the above layout point. In addition, according to the design requirements, it can also be selected on site.
3. Determine the baseline direction
When the starting point of the baseline is laid out, the direction of the baseline should be determined to lay out the accurate direction for the fixed network. As shown in Figure 2-2-2, place the instrument on the initial base point P, and measure the horizontal angle β p according to the control point K2 (β p is calculated according to the coordinates of the baseline starting point P and the control point K2 and the design direction of the baseline), so as to determine the baseline direction. In order to orient the baseline and check the direction of baseline measurement at any time, a "long-distance target" can be erected in the baseline direction. The baseline direction can also be determined by a compass as needed. Or determine the azimuth angle by the solar time angle method or the solar height method or the Polaris time angle method.
4. Layout base point
At the station, according to the baseline direction and the distance from the base point, the position of the base point is determined by photoelectric ranging, and at the same time, stakes or nails are nailed, dots are written and flags are inserted.
Figure 2-2-2 Layout of Baseline Direction
Change radio station
When the baseline continues to be extended due to inconvenient terrain conditions, the "front ruler" should choose a transfer station that is convenient for placement and timely observation. The distance between transfer stations is also measured by photoelectric method. The direction of the baseline after the transfer station can be measured in one or two positions if it is a folded baseline, and it is often measured by a mirror method or a turning method if it is an extended baseline.
Bury stones
In order to fix the survey network and abnormal position, so as to restore the survey network in the future and further arrange the geological, prospecting and geophysical work, it is necessary to bury the stone. The scope of stone burial includes the four corners of the survey network, the end of the baseline, abnormal points and other valuable points. At least two stone burial points should be ensured to be intervisibility on the same baseline. After burying the stone, you must draw a "point note", that is, draw a large-scale topographic sketch around it for future search.
7. Joint measurement
The main purpose of network survey is to obtain a unified coordinate system by controlling the survey network, and to provide mathematical basis for the coincidence of geological and geophysical results with topographic maps. The joint investigation sites are mainly stone burial sites. In addition, important geological signs (geological points, exploratory trenches, shallow wells and drilling holes, etc.). ) and railways, high-voltage lines and other ground features that affect the interpretation of anomalies should also be jointly measured. The joint survey method can use polar coordinate method, theodolite intersection method, traverse method and GPSRTK technology to determine the plane position of the joint survey point. Important points need to calculate coordinates.
8. Baseline verification
In order to check the correctness of baseline direction and length in time and evaluate the accuracy of baseline layout, it is necessary to check the route at an appropriate distance and end point. The verification method is usually close to or associated with a known point. The closure error shall meet the Code for Engineering Survey of Geological Exploration (GB/T/KOOC-0/834/KOOC-0/-200/KOOC-0/) and the Code for Engineering Survey of Geophysical and Geochemical Exploration (DZ/T0/KOOC-0/53-95) and SYT5/KOOC-0/. See table 2-2-2 for the tolerance requirements that should be met when laying the baseline with theodolite sight distance method.
Table 2-2-2 Verification Tolerance of Baseline and Measuring Line
(4) Survey line layout
After the baseline layout is completed and the inspection is qualified, the survey line can be laid. Generally, the survey line is closed between two corresponding baseline points, and the survey method is basically the same as the baseline survey, but the accuracy requirement is low. See table 2-2-2 for specific requirements. Generally, the method of extending the direction line adopts disc positioning, and the ranging adopts electromagnetic wave ranging or rope measurement.
Put the theodolite on one base point, aim at another base point, and turn it horizontally by 90 (270) to get the direction of the survey line. Then use the survey rope to arrange the survey points according to the specified distance (the distance between survey points in this exercise is 10m), mark each point with wooden stakes tied with red cloth strips, and indicate the corresponding point number on the red cloth strips. After the layout of survey line is completed, the closing difference of survey line must be measured on the spot to test the quality of work.
Method of crossing obstacles: In the process of survey line layout, there are often obstacles in the direction of survey line. Generally speaking, as shown in Figure 2-2-3, several methods can be used to overcome obstacles.
Figure 2-2-3 Several Methods of Crossing Obstacles
Rope measurement method: in the process of measuring distance by rope, first mark the distance between measuring points on the rope with red cloth strips; When measuring in a flat area, the distance can be directly measured by marking the distance between measuring points on the measuring rope; In areas where the terrain is not undulating, the horizontal distance can be measured by raising one end of the measuring rope; In areas with excessive topographic relief, the distance should be measured by measuring the inclination angle and calculating the horizontal distance according to the inclination distance.
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