Digital Earth Technology and Sichuan Highway Tunnel

The Civil Engineering Science Innovation Lecture of Southwest Jiaotong University (SWJTU) on the frontier topic of highway tunnel was held in room 1234 of the Civil Engineering Building at 15:00 on May 27, 2021. First, the host Gong yu gave audiences an introduction about the guests present: Lin Guojin, Academician of Tunnel and Underground Engineering Branch of Sichuan Highway Planning, Survey, Design and Research Institute Ltd., and Zhou Xi, deputy secretary of the Party Committee of the School of Civil Engineering (SCE), SWJTU, as well as counselor Shi Ying and Graduates Tang Rui and Tian Yuzhi.

Mr. Lin began his speech with the demand of highway tunnels, and introduced the application of digital earth technology to highway tunnels in simple terms. Here below are the main parts of the lectures:

First, Mr. Lin simply introduced the current status of highway tunnels in Sichuan province, where there are 10,000-kilometer highway to be constructed, of which highway tunnel to be constructed are 3,000 kilometers. With the emergence of numerous tunnel engineering, improvement of tunnel quality becomes the must-do research. Nowadays, as we enter an age of digital information and intelligence, the field of civil engineering urgently needs to combine with advanced technologies, among which digital earth technology comes into being. However, highway tunnel engineering still faces a bundle of problems such as how to integrate with multi-source data to select a location scientifically; how to conduct a topographic map research in remote areas; how to choose a rough scope for shaft and inclined shaft; how to recognize the environment surrounding construct-site, etc.

The core of digital earth is to simulate a virtual 3D earth, which supports simultaneous loading of images and topography. This system employs OpenSceneGraph (hereafter “OSG”) engine and OsgEarth topography and model data loading and rendering engine. Two problems must be solved to develop a digital earth system: 1. The match and mutual conversion between earth longitude and latitude coordinates with engineering coordinates. 2. Effective organization of massive multi-source surface image data (high-definition (HD) satellite film, aerial photography and LiDAR image) and elevation data to achieve fast access, stitching, rendering, display and roaming.

Later, Mr. Lin briefly illustrated the principles of Mercator projection and Gauss-Krüger projection, and introduced the different coordinate systems applied in the Digital Earth System in different display states. The digital earth adopts WGS84 latitude and longitude coordinate system, while engineering structures uses Gaussian projection coordinate system, and the large-scale GIS plane image resorts to the universal transverse Mercator coordinate system. And the word “integrated” in the so-called “integrated digital earth” means that the system has all the three coordinate systems. More than 4000 global coordinate projection parameters such as national 200, Xi'an 80, Beijing 54 and WGS84 are embedded in the digital earth, and the processing of massive multi-source images has already been realized.

Then Mr. Lin detailed the application of digital earth in civil engineering. Here below are the main applications: 1. Downloading, stitching and rapid production of HD image route scheme report for a given area of satellite imagery. 2. The generation of contour line topographic map (DWG format) on any given area at any scale (1:10000), and it can be overlaid with HD satellite images (or aerial HD images). 3. Through the search of well location of inclined shaft, the optimization of cross section, economical and rational ventilation methods and optimal ventilation shafts, we can significantly reduce the costs and energy consumption in the tunneling. 4. The generation of arbitrary profile ground line (pile number, elevation data). 5. The integration of multi-source high-accuracy mapping results (DEM DOM), the parametric model display of road, bridge and tunnel, and the Internet-based field investigation. 6. We can investigate topography through digital earth roaming in arbitrary path and obtain instant information about the tunneling environment to rationally arrange the construction and temporary road, and learn the demolishing and resettle status and optimize muck site selection. 7. Driving simulation: achieving digital earth roaming at any speed and at any viewpoint height along a designed route. 8. Conducting a “field investigation” in areas inaccessible to personnel on the digital earth. 9. Supporting file formats such as dxf, kml, etc. 10. Parametric design of highway tunnel.

When it came to the outlook of digital earth, Mr. Lin mentioned the following points: 1. Intelligent location; 2. Ray tracing algorithm; 3. Building a physical digital earth by overlying 3D geology information; 4. BIM model stratum terrace and underlying terrace collective design.

Finally, there was a Q&A session, and Mr. Lin patiently answered all the questions for the students. One student asked about the efforts needed for entering the provincial institute, then Mr. Lin gave his advice: students should focus on their professional qualities, and they would be more likely to be selected if they are interested in solving problems in highway tunnels, for example, disaster prevention and rescue system design, rock burst deformation and so on; furthermore, internship experience is also an advantage. The second student asked how to do academic research? Mr. Lin said that interest is the greatest motivation, and his path of academic research started from his graduation project. Students need to cultivate their greatest interest in some certain niche area, which would reward them a good result in the long run. The last student exchanged his opinions with Mr. Lin about the future of domestic BIM technology, and pointed out the drawbacks existing in current BIM design. Mr. Lin hoped that the new generation can start from BIM underlying software so as to promote the Chinese BIM in engineering.