1. Road line selection
Road line selection is to select a road center line between the starting point and the end point of the road planning plan that is technically feasible, economically reasonable, and can meet the usage requirements. Line selection work faces a very complex natural environment and socio-economic conditions, and requires consideration of many factors.
1. The purpose of road line selection and task
The purpose of road line selection is to select the central line position of the road on the ground or paper based on the nature, task, level and standards of the road, combined with the terrain, geology, landforms and other conditions along the line, and combine the three factors of flat, vertical and horizontal, and select the central line of the road on the ground or paper. The main task of road line selection is to determine the direction of the road and the overall layout of the , specifically determine the intersection location of the road and the elements of the selected road curve, and determine the plane position of the route through the selection of lines on paper or on-site.
2. Road line selection requires
route is the skeleton of the road. Its quality is related to the function of the road itself and whether it can play its due role in the road network. In addition to natural conditions, the factors affecting route design are also subject to many social factors. Line selection should comprehensively consider a variety of factors and properly handle the relationships in all aspects. The basic principles are as follows:
1) At each stage of the route not being considered, various advanced means are used to conduct in-depth and meticulous research on the route plan, and based on multi-scheduling and comparison, select the best route plan.
2) The route design should ensure that driving safety, comfort and speed are small, the number of projects is low, the cost is low, the operating costs are cheap, the efficiency is good, and it is conducive to construction and maintenance. When the project volume does not increase much, higher technical indicators should be used as much as possible. Minimum indicators or low-limit indicators should not be easily used, nor should high indicators be pursued one-sidedly.
3) The line selection should be coordinated with the basic construction of farmland to occupy less land, and should not occupy high-yield fields, economic crop fields or economic forest gardens as much as possible.
4) Highways through scenic spots, scenery and historical sites should be coordinated with the surrounding environment and landscape, and appropriate care should be taken into consideration. Pay attention to protecting the original natural state and important historical relics. When selecting lines, in-depth surveys should be conducted on engineering geology and hydrogeology to find out their impact on highway projects. Seriously undesirable geological areas such as landslides, collapses, rock piles, mudslides, karst, soft soil, and sludge, as well as special areas such as deserts and permafrost, should be treated with caution. Generally speaking, the route should be avoided. When it is necessary to pass through, the appropriate position should be selected, the crossing range should be narrowed, and necessary engineering measures should be taken.
6) Line selection should pay attention to environmental protection, pay attention to issues such as the impact and pollution caused by road construction and automobile operation. Specifically, pay attention to the following aspects: ① The possible impact of the route on natural landscapes and resources; ② The impact of land occupation and demolition of houses; ③ The impact of the route on existing facilities such as urban layout, administrative divisions, agricultural farming areas, water conservancy and irrigation systems; ④ The impact of noise on residents; ⑤ The pollution and impact of automobile exhaust on the atmosphere, water sources, and farmland; ⑥ The impact on the natural environment, resources, and pollution prevention and control measures and their countermeasures are implemented.
3. Road line selection steps
Selection of a road route is achieved through the process of from shallow to deep, from outline to local, from overall to specific, from surface to lead to line. It generally requires the following 3 steps:
1) comprehensive layout. Comprehensive layout is a global work to solve the basic direction of the route. It is to find possible "routine belts" at the starting and end points and the strongholds that must be passed in the middle, and determine some large control points, which can be connected to form the basic direction of the route. For example, between the starting and ending points and the stronghold, you may go along a certain river or cross a certain ridge; you may go along one shore or the other shore. These are all issues with route layout.
2) Arrange paragraph by paragraph. This is the work of further encrypting control points and solving local route solutions based on the basic direction of the route.That is, between large control points, combined with terrain, geology, hydrology, climate and other conditions, small control points are determined one by one.
3) Specific line. This is the work of repeatedly threading and inserting points between small control points arranged one by one, according to technical standards and natural conditions, based on technical standards and combined with natural conditions, comprehensively considering the three factors of flat, vertical and horizontal, repeatedly threading and inserting points, and specifically determining the location of the route. This step is more in-depth, more detailed and more specific. The specific line setting is completed by the line selection group during detailed measurement.
4. Road line selection method
Select the Road midline position according to its specific practices, it can be divided into three methods: real-time line selection, paper line selection and automated line selection.
1) Field line selection
Field line selection is a method by which the line selection personnel conduct on-site survey and measurement on site according to the requirements of the design task book, and after repeated comparisons, they directly select the route.
The characteristics of this method are simple and practical; it is easy to grasp the geology, terrain and landform conditions on the spot, and the solutions made are realistic and reliable; when setting lines, you generally do not need large-scale topographic map . However, this method has a lot of work in the field and high physical labor intensity. Field measurement and installation work is greatly affected by climate and seasons. At the same time, due to the limitations of vision and the influence of terrain, landforms and land objects, the overall layout of the route has certain one-sidedness and limitations. Therefore, field line selection is generally only used on highways with lower grades and relatively clear plans.
2) Select line on paper
Select line on paper is on the measured topographic map. Comparing route layout plans, thereby determining routes on paper and then laying lines on the ground. The characteristics of this method are that the field workload is small and the measurement and setting speed is fast; the measurement and setting line are not disturbed by natural factors; the overall situation can be viewed indoors, combined with the terrain, terrain, and geological conditions, and comprehensively consider the three aspects of flat, vertical and horizontal factors, so that the selected route is more reasonable. However, there must be a large-scale topographic map for the line setting on paper, and the measurement and installation of topographic maps requires a large amount of workload and more equipment. The line selection on paper is mostly used for roads with high grades and complex terrain and land objects.
3) Automatic line selection
With the rapid development of aerial survey technology and electronic computer technology, an automated line selection method combining aerial survey and computer has emerged. The basic method of automated line selection is to first measure the aerial survey pictures using aerial survey methods, then establish a digital terrain model based on the terrain information (ContextCapture real-life modeling software), convert the requirements of line selection design into mathematical models, input the design data into the computer, and the computer automatically selects, analyzes, compares, and optimizes according to certain programs, and finally outputs all design charts through an automatic plotter and printer.
Automatic line selection uses electronic computers and automatic plotters to replace manual labor to do a lot of tedious calculation, drawing, analysis and comparison work. This can make the selected route plan more reasonable, and save manpower, material resources and time, which will become the development direction of road line selection in the future.
2. Road terrain modeling
through tilt photography to shoot the road line selection range, obtain relevant road data, and then use the real-life modeling software ContextCapture to generate grid models and road cross-sections, and extract road terrain and fracture lines through processing. In addition to the above functions, the real-life model built through ContextCapture can not only directly generate orthophotos and digital surface models, but also perform earthwork calculations. The model browser of ContextCapture can directly measure geomorphic coordinate points, distance, area and volume.
Let’s take a look at the functions of ContextCapture:
ContextCapture is a software that can automatically generate detailed three-dimensional real scene models from simple photos and/or point clouds. ContextCapture's high compatibility enables accurate and seamless reconstruction of various objects and data sources, from centimeters to kilometers, shot from the ground or from the air. As long as the resolution and accuracy of the input photos are sufficient, the generated three-dimensional model can achieve infinite fine details.
1) Integrated georeference data
ContextCapture can provide local support for various types of location data including GPS tags and control points. It can also import any other positioning data through positioning/rotation import or full block import, enabling precise measurement of coordinates, distances, areas and volumes.
2) Automatic aerial triangulation and three-dimensional reconstruction
Once automatically recognizes the relative position and direction of each photo of , the aerial triangulation results can be fine-tuned by adding control points and editing connection points to maximize geometric and geospatial accuracy. The optimized 3D reconstruction algorithm generates accurate 3D models and image textures for each grid with unrivalled accuracy. ContextCapture ensures that each 3D grid model vertices are placed in the optimal position, so fewer defects can reproduce finer details and sharper edges, greatly improving geometric accuracy.
3) Generate two-dimensional and three-dimensional GIS models
With the help of ContextCapture, accurate georeferenced 3D models in various GIS formats can be generated, including real projection images and new Cesium 3D Tiles, and export tile ranges and empty three results to KML and XML. The coordinate system database interface provided by ContextCapture ensures data interoperability with GIS solutions. Select from over 4,000 spatial reference systems and add user-defined coordinate systems. Moreover, ContextCapture will automatically adjust the resolution and accuracy of the model based on the resolution and spatial distribution of the input photos.
This means that ContextCapture can handle scenes with uneven resolution without sacrificing overall efficiency to preserve some higher resolution scene areas.
4) Processing the real scene model
ContextCapture can quickly and easily process grid models of any scale, as well as the generation of cross-sections, the extraction of terrain and fracture lines, and the generation of orthographic images, three-dimensional PDFs and iModels. It integrates grid models with GIS and engineering data to enable intuitive search, navigation, visualization, and animation of this information in the visual environment of grid models.
5) Generate and process large scaleable terrain models
ContextCapture can generate very large scaleable terrain models from a variety of sources, including point cloud , break lines, raster digital elevation model and existing triangulated irregular networks. By synchronizing with the original data source, the scalable terrain model can be updated to the latest in real time. The value of this is to have a global, latest and comprehensive representation of all your data and to perform analysis using various display modes, as well as generate animations and visualizations.
ContextCapture software details:
If you have a real scene modeling project, or are interested in the real scene modeling software ContextCapture, welcome to follow the WeChat official account of "Ai San Dimension Technology" and contact us.
