Method Of Refined 3D Model Construction Of Space-ground Integration

With the development of photogrammetry and computer technology,3D reconstruction has been widely used in digital city,smart city,cultural relics archaeology and other fields.And the upgrading of various applications has brought out the increasing demand for the refinement of 3D models in various industries,thus constructing 3D model efficiently and accurately has become a research hotspot.The UAV low altitude oblique photogrammetry technology has many advantages such as high efficiency and low cost when acquiring large area data,making it a mainstream method of real-world 3D modeling.Oblique photography obtains image data from vertical and oblique multiple angles simultaneously through one vertical lens,four or more oblique lenses.Compared with traditional aerial photogrammetry,it can obtain richer structure and texture information of the object side,and meets the needs of high-quality 3D modeling.However,due to the limitations of UAV flight height and aerial photography acquisition angle,the structure and texture of the ground objects near the ground and the occluded area are lost or insufficient,and the phenomenon such as structure and texture loss and distortion will appear when the real 3D model of this part is zoomed in.Aiming at the problems of oblique photography,different types of ground objects are classified in this paper,a method of optimizing the 3D model of oblique photography by using close-range photography and 3D simulation modeling software is proposed,the refined 3D modeling method of space-ground integration is discussed,and the optimization effects are evaluated quantitatively and analyzed qualitatively.The main contents of this paper are as follows:(1)Constructing the real-world 3D model of oblique photography and analyzing the accuracy of the model.In this paper,the plane and elevation accuracy of the 3D model of oblique photography are both 2~3cm,which is much higher than the level I requirements in the Product Specification of 3D Geographic Information Model Data.Cutting off the non-modeled area and modifying the deformation together with loopholes of the water surface as well as buildings through DP-Modeler software.(2)For the objects with large size,complex structure,obstacles around and easy to be covered by low altitude photography,the method of space-ground integration of close-range photogrammetry modeling is used.For buildings with high-rise structure and tall statues,adopting the method of low-altitude stereo ring-shooting of close-range photography modeling.For the low objects near the ground,with complex structure and many contour feature points,the models are constructed by the methodof ground close-range photogrammetry.The 3D model of oblique photography is optimized by close-range photography.The experimental results show that the texture quality of the local model of oblique photography is significantly improved by using the method of optimizing oblique photography by close-range photography,and the geometric accuracy of the local model reaches centimeter level.(3)Aiming at the thin and high independent features such as streetlights,power poles,flagpoles and models of leveling rods,as well as small-sized features near the ground with relatively regular structure and complex texture,using 3D simulation modeling software to build the models.The 3D model of oblique photography is optimized by using 3D simulation modeling software.The experimental results show that the fusion effects of models constructed by 3D simulation modeling software and the real 3D model of oblique photography are good,the geometric structures of 3D simulation models are fine,and the textures are delicate and real.In this paper,there are 39 figures,9 tables and 106 references.