The Method Of Buildings Monomer Based On UAV Oblique Photography Scene Modeling

"Digital City" and "Smart City",which are based on 3d model of city scene,have become inevitable for the construction of city operation and management,also are the main content of the city 3D GIS.Therefore,for large-scale urban scene,how to quickly and efficiently build the 3D model is a challenge in the field of surveying and mapping geographic information.Nowadays,the rapid development of Oblique photogrammetry technology provides a new technological approach for the construction of urban scene model.Buildings are the most important objects in the city scene,however,the scene model made by Oblique photogrammetry technology is a whole,which can well meet the visual sense,but it can't realize that computers recognize and give attributes to target objects and isn't beneficial to the later GIS application.Therefore,also needing to achieve the goal that semantic segmentation of target objects,especially the building monomer modeling.At present,building monomer modeling mostly adopts the method of interactive delineating and edit in the whole model,which obviously has big workload,low efficiency,and is difficult to meet the requirements of large-scale urban rapid,efficient modeling.Based on the above problems and challenges,in this paper,on the basis of the automatic generation 3D scene model,with the goal of building model automatic extraction and monomer in the whole 3D scene model,carrying out the related research,whose main content is as follows:(1)Building extraction based on image features and rough segmentation of 3D modelThe geometric and texture features of buildings in scene digital orthophoto map(DOM)are analyzed in detail.On this basis,a method for sketchy positioning of buildings is proposed.The scene DOM is processed to acquire and filter out the outlines of the buildings,then,minimum inerratic bounding rectangles are generated for the outlines of the buildings.Based on this,the image coordinates of the bounding rectangles are obtained and converted into geographic coordinates.Then the bounding rectangles are used as the constrained region of the geographic location to initially segment the 3D scene model to obtain rough building monomer models.(2)Purification of building monomer model based on geometric featuresThrough the analysis of the overall and local geometrical characteristics of the building model in the 3D scene model,a method for selecting and retaining the triangle facets of the building using the geometric features of the triangle facets is proposed.The normal vector of triangle facet is used to represent the direction of the triangle facet,and the direction of the facet is classified according to the reference direction.The topology adjacency relation of the triangle facet is constructed.The normal vector of triangle facet and the topology adjacency relation between facets are used to design the 3 kinds of patterns to describe the roughness of the area where the center triangle facet is located from simple to complex.Geometric features based on the roughness criterion,facet type,and facet height are used to screen the model triangle facets,and the triangle facets corresponding to the building features are retained.The method of adjacent facet grow is used to reconstruct a new whole with retained triangle facets,then filtrating out and retaining the building models according to the overall characteristics of the building,so as to obtain relatively pure building monomer models.(3)Organization of building monomer model dataIn order to facilitate the storage,management,repair,and application of monomer model data at a later stage,a single file is used to express a monomer model.After the building models are filtrated out and retained,a method of dual-collection parallel indexing is proposed to accurately adjust and organize monomer model data,so as to achieve the expression of building monomer model data.(4)Design and development of a prototype system for building monomer modeling based on 3D scene modelBased on the realization of the above content,a prototype system for building monomer modeling based on 3D scene model is designed and developed.The system can complete the identification and location of building outlines in scene DOM,and can complete segmentation of a 3D scene model to obtain rough building or similar building model based on the position information of the building outlines,and can complete purification of the rough monomer model to obtain relatively pure building monomer models according to the 3D spatial geometric characteristics of the buildings,and can use a single file to organize building monomer model data.