In Vietnam, Lidar data (aerial laser scanning technology) with average point density has been collected on a large scale, through projects to build 1/2,000 base geodatabases – 1/5000 for urban areas and projects to build digital models of elevations in the delta and coastal areas to respond to climate change. One of the value-added products that can be built from this valuable data source is a 3D map for urban areas that has been researched by the National Center for Remote Sensing.
Project of building digital model of delta’s elevation to respond to climate change using Lidar and remote sensing
In recent years, 3D maps have been built more and more for urban areas towards providing background data for urban management. Lidar technology is gradually becoming more popular with high-resolution remote sensing images that complement each other and open up the possibility of improving the detail of objects of 3D maps. Based on research topics on Lidar data processing methods and high-resolution remote sensing images and displaying the contents of 3D maps, the general process for 3D mapping is proposed with 25 practical steps presently. Depending on the characteristics of the input data, especially the density of Lidar points, it may be necessary to adjust the implementation plan for some small stages of the process.
The project has built a process to create 3D maps from Lidar data and high-resolution remote sensing images based on theoretical studies, experimental results and experiences from 3D mapping projects. cities in the world. This procedure is tested with TP area mean density lidar data. Bac Giang and completed in some details. The establishment process starts with decoded Lidar data and high- resolution remote sensing images based on 3 groups of software: MicroStation and TerraScan for processing and extracting information from Lidar data; SketchUp for highly detailed home modeling; ArcScene, ArcGIS for background geodata organization and aggregate display of the final map product.
Through the trial process of building 3D maps in an area of the city. Bac Giang with positive results has confirmed the feasibility of the proposed map content and establishment process in terms of our country’s technology.
The project has achieved the two main goals set out, the results of the project can be widely applied to establish 3D maps for urban areas in our country and coordinate with localities to put them into direct application. in urban management.
Research and experimental results show that, with medium-density Lidar data and high-resolution remote sensing images, it is possible to establish a 3D urban map with the highest level of detail in the range between LOD2 and LOD3. according to international standards. However, due to a lot of work, the implementation is still done manually, so the small roof details cannot be shown.
In order to really implement the urban management model with this type of map, it is necessary to modernize the modeling of houses from Lidar data on TerraSolid software for urban areas of our country. a lot of manual practice, leading to some intricate details of the roof not being shown.
Wanting to use this system to ensure the speed of displaying 3D maps on ArcScene, requires a highly configurable computer because choosing ArcScene as the output software allows homogenizing 3D map products with 1/2000 databases, 1/5000 currently on ArcGIS.
The test product launched using the available symbology of ArcGIS basically meets the general expression requirements, but some symbols in form are not very close to the reality of our urban areas. Therefore, it is necessary to continue to complete research and develop standards for the construction of urban 3D maps from Lidar data. Coordinate with the locality to build a 3D map for a complete urban area and put the urban management applications of this product into practice as a model. At the same time, conduct research on the scientific basis, data structure of the 3D cadastral map and accompanying legal frameworks.