Research on Fast site selection and 3D Simulation

At the 1993 International Radio General Assembly meeting, ten Chinese writers, including China, proposed to jointly build the Square Kilometer Array (SKA) program with a reception area of one square kilometer. Since 500, a research team headed by the National Astronomical Observatory has started the SKA pilot project-five-hundred-meter Aperture Spherical teltelescope (FAST) preliminary research work on construction. Using the karst depression as the support condition for the Main reflector of the 500 m large radio telescope and its candidate site, and building a radio telescope array consisting of more than 40 units in Guizhou, it was creatively proposed by China, it is also one of the fundamental differences between the SKA China engineering design scheme and other national programs.

First, using satellite remote sensing images and topographic maps and other related data, through computer image processing and spatial feature interpretation of remote sensing images, Guizhou is the center to find the SKA peripheral points within 1000 kilometers, A large number of sinks suitable for building ska have been found in the south of Guizhou. Then, based on historical data access, Remote Sensing Image Analysis and engineering geology, hydrological geological site survey and measurement methods, this area has carried out multi-disciplinary site evaluation for its natural geography, control factors of landform development, morphological characteristics of land areas, hydrology, engineering stability, meteorology, and electric wave environment, we found more than 300 sinks that can be used to build SKA, and selected the largest nest and shangjianchong.

Through a detailed analysis of the structural, engineering, and hydrological geological data within the two regions, it is found that there are no recent fractures in the middle and new areas of the region. Other faults and joints are filled by the tungsten and block, and the cement is solid. The geological structure is simple, the original structure of rock mass remains intact, the rock mass structure is tight, the texture is uniform, and it has good engineering geological properties.

Then, the high-resolution Quickbird remote sensing images, a-topographic map, and telescope parameters are used as data sources. The optimal DTM and fast sphere crown fitting are studied, in the 3D simulation scenario, the quantity of excavators is calculated as the index of construction cost accounting. The depth, height, and terrain of each slice are queried to check the construction difficulty. A three-dimensional scene and telescope model were created for the surrounding environment of the big nest, and the digital elevation model and the telescope reflected spherical space model were used to calculate the excavation quantity in real time, query and obtain the height and depth of each slice. The method for establishing a telescope spherical space model is to first project the whole telescope model to a square grid with a cell size of 1 meter. Then, the distance from each cell to the center of the entire grid is calculated. After comparing the size with the open radius of the telescope, it is marked which grids are occupied by the projected telescope. Finally, the telescope surface height values corresponding to each cell are calculated based on the telescope spherical radius, open radius, and angle. The statistical method of real-time earthwork quantity is to determine the coordinates in the top left corner of the reflected spherical space model in the terrain grid, and then calculate the distance between the reflected spherical sphere and the land, the distance between the sphere and the land area is determined as the filling depth, and the distance between the land area and the earth area is determined as the excavation height. Accumulate the product of Fill Depth and area of each cell of the reflected sphere, and the product of each excavation height and area respectively, the total filling amount and the total digging amount can be obtained.

The 3D simulation results show that the 3D big nest scene drawn based on the digital elevation model and high-resolution remote sensing image can better reflect the three-dimensional terrain, intuitively express the parameters related to the site selection of the nest worker fast. Understanding the entire Engineering Environment from different perspectives, observing and planning a wide range of natural environments around the site, landform form, etc., achieving the purpose and effect that traditional means of expression cannot achieve. In the three-dimensional scenario of the nest, people can move the three-dimensional model of the radio telescope with an opening diameter of 500 meters and a angle of 120 degrees at any time, so that people can better study the relationship between the large-scale telescope and the surrounding environment, including the fit of the valley, the need to relocate and consolidate the land, and the need to complete earthwork excavation, depth and height of each slice. In real-time simulation environment analysis, the calculation result of the earth excavation is highly accurate, with an error of only 0.48% compared with the theoretical calculation value. Therefore, the 3D simulation environment system can provide an effective tool for selecting and locating fast hosts.

 

Site Selection

The main factors that affect the site selection of large radio telescopes are summarized as follows:

1. ry condition: the ry condition reflects the fitting degree between the telescope sphere crown and the karst depression, and determines the total number of holes to be dug. The better fit between the land area and the Ballon crown, the smaller the quantity of excavators. In addition, the closed land area has favorable conditions for reducing the amount of excavation and wind load. The more mountains surrounded by the closed land area, the more favorable it is.

2. Geological Conditions: site stability will affect site safety. A good material base and rock mass structure are the most important indicators for measuring the stability of fitting the ball crown construction and bottom slabs. Natural Geological Disasters with typical characteristics of landslides, collapse, and debris flows often directly endanger the safety of engineering construction and human life and property. They are necessary factors for environmental evaluation of major projects. During the development and evolution of the land, the development of the karst water system, the development of the bottom drop water cave, and the formation of the underground dark river are all important factors that directly affect and control the water excretion in the land.

3. meteorological conditions: the terrain around the land area has a great impact on the micro-climate, and the changes in temperature and precipitation are very complicated. This directly affects the structure design and normal use of the large radio telescope.

4. Radio Environment: Because radio astronomy generally receives extremely weak celestial radio signals from the universe. Therefore, at the site of the telescope, there cannot be any other "slight" radio interference. Otherwise, the power of the large radio telescope will be lost.

5. socio-economic conditions, including necessary conditions for the construction and maintenance of large radio telescope projects such as transportation, electricity, and human resources.

Therefore, it is a complex system analysis process to select a suitable large radio telescope candidate site in Guizhou's numerous karst valleys, in essence, it is the process of finding the optimal combination of the Site Conditions in the mutual constraints of the Land Geometric conditions, engineering conditions, geological conditions, meteorological conditions and radio waves. The following is a site selection method for the large-scale radio telescope in Guizhou's karst area.

The survey of land area in Guizhou Province adopts the method of combining indoor research and field investigation: (1) using geological map and aerospace remote sensing images, according to the distribution characteristics of carbonate rocks, exclude areas where the development of the karst depression is impossible. Based on the large scale topographic maps and Remote Sensing aerial data, the authors selected multiple land areas based on the geometric conditions of the large radio telescope. (2) On-site investigation of multiple land areas, focusing on the investigation of geological disasters such as formation, lithology, occurrence, rock structure, landslide, debris flow, and karst collapse, combined with the Geometric Conditions of the previous step, make a qualitative evaluation of these regions; (3) draw a map of the candidate sites in Guizhou based on the primary area, and determine the key concentration areas in the area to guide further site selection.

Starting from 1994, the above method was used to search for the SKA peripheral points within 1000 kilometers centered in Guizhou, for the natural geography, control factors of landform development, morphological characteristics, hydrological geology, engineering geology, meteorology and electric wave environment of the karst area in southern Guizhou, after conducting a multi-disciplinary site evaluation, we found more than 300 sinks suitable for building SKA in southern Guizhou. Among them, the big nest and shangjianchong areas are selected for fast.

3-Dimensional Simulation of big nest

Virtual reality (VR) is a new comprehensive technology that emerged at the end of the 20th century. It integrates the latest development achievements of multiple branches of information technology, including digital image processing, computer graphics, artificial intelligence, multimedia, sensors and measurement, network, and parallel processing technology, it provides powerful support for creating and experiencing the virtual world, thus greatly promoting the development of computer technology. Because the virtual simulation system can "reproduce" planned projects in real time, many imperceptible design defects can be discovered in a timely manner, this greatly reduces irreparable losses and regrets caused by incomplete planning. The Virtual Simulation System for site selection planning has upgraded the expression of site selection planning from the original traditional model technology to the new digital technology stage, this solution solves the problem of inintuitive, true, and accurate performance and evaluation of site selection projects by using traditional methods. This also improves the quality of site selection evaluation.

The nest region is located in the southern region of Guizhou (e106 ° 51 '20 ", n25 ° 39 '10"), where karst is strongly developed and is a deep depression of Karst Peak. The bottom elevation of the land is 841.2 m, and the whole land area is relatively closed. The east, north and southwest of the land area have three prominent peaks. The highest mountain altitude is 1187.5 m, the lowest mountain head is 1104.1 m, and the Low saddle is 900 m. Based on the site selection work, we further study the optimal DTM and fast sphere crown fitting to complete the simulation of the fast site selection, and establish a digital elevation model (DEM) based on) with high-resolution remote sensing images, the environment around the nest is 3D, and functions such as display and browsing of 3D scenes, interactive operations, and information query are developed. This allows you to calculate the number of excavators in real time, query the height and depth of each node.

Simulation Technology Route

The overall technical route 1 is described as follows.

1) Data Processing: uses high-resolution Quickbird remote sensing images and a--Scale Topographic Map as the basic data source. Digital Topographic Map to obtain the absolute elevation of each contour line. Because the equal height of the original topographic map is 5 meters, the DEM with a grid size of 1 meter must be obtained after re-sampling.

2) After the remote sensing image is corrected and processed as a landscape map, a three-dimensional terrain model is generated Based on DEM data and the dimension is used as the basis in the modeling tool environment (3 dstudiomax) after generating the telescope 3D model, prepare for the synthesis of the entire scenario.

3) Based on the telescope parameters, the reflected spherical space model is calculated and stored in two-dimensional arrays. It is used as a prerequisite for excavation calculation, node padding calculation, and depth calculation.

4) after adding all models in the scenario to the 3D simulation driving engine, the mobile telescope model combines the digital elevation model and the reflected spherical space model, real-Time Calculation of information such as the quantity of soil samples and specific geographical locations.

 

Calculation Method of excavation earthwork

If the terrain length and width are M * n meters, the initialized array is height [N] [M]. The telescope parameter is angular 2 and the opening radius is r meters. The radius of the entire sphere can be considered as R/sin meters.

The open diameter of the telescope is r meters. The open circle is placed on the square of an R * R. The direction of the open circle is the same as that of the terrain, that is, the horizontal direction of the X axis points to the east, the vertical Y axis points to the positive south. The purpose is to mesh the telescope in the form of the same as the terrain DEM, that is, each 1 meter * 1 meter square has a height value, the lowest point is 0 meters, the highest point is the edge, is R/sin-R * CTG.

To match the terrain data, the whole telescope model needs to be gridded to calculate the number of excavators and determine which cells are occupied. The processing process is that the whole telescope is first projected into the square, then the projected image is a circle with a diameter of 2R. The criterion is calculated by dividing the vertex into four areas. The distance between the vertex and the center in the lower right corner of a small grid in the northwest corner is less than R. If it is less than R, the small lattice is considered to be within the circle range; if it is greater than or equal to R, it is considered to be out of the circle range. The northeast corner area uses the vertex in the lower left corner of the small lattice; the southwest corner area uses the vertex in the upper right corner of the small lattice; the southeast corner area uses the vertex in the upper left corner of the small lattice, which is processed in sequence; then, calculate the height value of the lattice within the circle range, and mark the lattice outside the circle range. The mark is the height value assigned to a maximum value (9999 ). The formula for calculating the grid height within the circle range is to obtain the distance a from each cell to the center of the circle obtained during the discriminant calculation. The radius of the whole telescope model sphere is R/sin, then

Height

When moving the telescope in real time, the three steps are 1 meter. In this case, the excavation calculation is performed through the calculation of the Raster Data of the terrain DEM and the telescope model. Because the bottom area is 1 m² square meters, the volume is equal to the difference between the terrain and the telescope height. If the terrain height is greater than the telescope height, it is the amount of excavation. If the terrain height is less than the telescope height, it is the amount of filling. The difference value on each grid is accumulated to obtain the total amount of excavation. The process of moving the telescope can be recorded. The steps in the three directions are xcount, ycount, and zcount. Because the first position in the upper left corner of the telescope relative to the coordinate of the terrain square is (x0, y0 ), after the telescope moves, the corresponding position in the upper left corner is changed to (x0 + xcount, y0 + ycount ). The process of calculating the quantity of excavators is a dual loop, with the number of R cycles per time. After the first cycle, the height of each basic cell of the telescope is obtained. The height value is composed of three parts, that is, the height value (between 0 and R/sin-R * CTG ), the terrain height that is placed at the lowest point of the telescope at the initial position. The height adjusted by the user (that is, the zcount value ). In the second cycle, the elevation value of the terrain corresponding to the telescope is obtained. The range of this area is in the upper left corner (x0 + xcount, y0 + ycount), and in the lower right corner (x0 + xcount + R, y0 + ycount + r. After this rectangular area is obtained, it is equivalent to the index to be used in the array height [N] [m] to obtain the elevation value.

Technical Route:

 

Proposed and Information Query

In the upper-left corner of the telescope, the coordinates are (x0 + xcount, y0 + ycount), which is () relative to itself. This is the case of moving, so xcount is added, ycount; in turn, if the click gets the location on the terrain is (TX, Ty), for the vertical direction on the telescope itself is (tx-x0-xcount, ty-y0-ycount ), you need to make a judgment to check whether the two values are less than 500. Otherwise, there will be no telescope patch on the top.

After obtaining (TX, Ty), it is equivalent to obtaining the index of the Terrain elevation data array, so as to obtain the elevation value, also can calculate the Longitude Latitude value; after obtaining (tx-x0-xcount, ty-y0-ycount, it is equivalent to obtaining the index of a cell in the telescope to obtain the telescope height value. By comparing the two, you can calculate and query the quasi-and position information such as the height and depth of each node.

 

Conclusion and discussion

Based on the digital elevation model and high-resolution remote sensing image, the big nest embedding 3D scene can better reflect the three-dimensional terrain and is very intuitive. Compared with the use of contour lines to represent terrain forms, it has its own unique advantages, which is closer to people's intuitive vision. In the three-dimensional scenario of the nest, people can stack and move the three-dimensional model of the radio telescope with an opening diameter of 500 meters and a angle of 120 degrees at any time, so that people can better study the relationship between the large-scale telescope and the surrounding environment, including the matching with the valley, the area where the Earth needs to be dug, and the location of the maximum depth and height of the Earth, it is meaningful to migrate the whole project environment from a high-altitude perspective and observe the natural environment and landform pattern around the planned site selection, it is also impossible for traditional means of expression.

In the big nest complex 3D scenario, based on the mathematical basis of the terrain-digital elevation model, the project reference data and engineering quantity estimation are completed on the basis of the design size of the telescope. After the telescope location is determined, data such as the excavation quantity and maximum excavation depth and height of the project are automatically calculated.

It is very difficult to manage these complex projects effectively. The conventional data management method is the combination of databases and floor plans. This method can only represent the location and attribute of the project, and cannot display the overall picture of the project. It is not vivid enough and lacks multimedia technology, this article tries to use advanced computer geographic information technology and simulated reality technology to visually express spatial information in the form of a three-dimensional model to give people an immersive feeling, information is displayed based on spatial images and multimedia means. The natural landscape and project planning and construction conditions are reproduced in a true, intuitive, and dynamic manner. Information that is difficult to obtain through conventional methods is obtained, the precise positioning and description of the project in a three-dimensional environment can give the decision makers a global and clear understanding. In the next step, we plan to overlay various special features on a three-dimensional model and perform model and feature attribute overlay analysis. This will help us make scientific decisions on project construction and management.

References

1. South rendong 500 m spherical reflector Radio Telescope fast china science g series physics and mechanics astronomy 2005, 35 (5): 449 ~ 466

2. Nan r d, Peng B. A Chinese concept for the 1 kmradio telica. Acta Astronautica, 2000, 46 (10 ~ 12): 667 ~ 675

3. Site Selection Methods for song jianbo, Liu Hong, Wang Wenjun, Peng Bo, and nanrendong radio telescope in Guizhou Karst Region: Earth and environment vol.33, No. 3 ~ 68

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