Study On 3D Spatial Visibility Analysis Methods Of City Based On UDEM

Urban space is an open space for urban residents' activities,and the construction of urban space is increasingly pursuing more scientific and higher quality.Three-dimensonal(3D)Spatial Visibility Analysis transforms visual perception of urban space to quantitative indicators,so as to provide a large amount of quantitave visual information of 3D space.It can provide scientific decision making basis for planning and regulating of urban spatial morphology and layout structure.Urban space is regarded as the research object,and a 3D visibility analysis method based on GIS is proposed from the perspective of vision.In the first place,the basic concept of 3D visibility analysis is summarized.The next time,the static viewpoints and dynamic viewpoints are selected and the maximum visible radius is determined according to the geographical features of urban space.Finally,the quantitative indicators of visual information,such as the visible distance,the area of the visible areas,and the value of the effective visble distance are calculated using the technology of the intervisibility analysis and viewshed analysis based on the 3D spatial visibility analysis model.A case study of Shahekou District in Dalian city is carried out.The visble distance,visible area and effective visible area are quantified to the viewpoints.The visual conditions of the main viewpoints are analyzed and discussed according to the calculation results,and the reliability of 3D visibility analysis method of urban space is proved by field investigation.It is concluded that the most direct factor affecting the visibility is the elevation of terrain surface,the difference in the height of the buildings in the surrounding environment of the viewpoints is also a very important factor.Areas with high elevations and the high buildings are easy to block the line of sight,but it is also better to observe the surrounding environment in such areas.At the same time,the design and development of 3D visibility analysis system is completed based on.Net technology and SuperMap i Objects.Net API.The system provides functions of intervisibility and viewshed analysis of 3D terrain,intervisibility and viewshed analysis of 3D scene and dynamic viewshed analysis.In particular,the dynamic viewshed function can perfectly simulate the visual perception of people walking on the road,and the dynamic display effect of 3D visibility analysis really comes true.The results of calculation and analysis of each quanitative indicators show the visibility of the viewpoints.And the 3D visual analysis and visual expression of 3D visibility analysis results are both realized.3D visibility analysis method of urban space proposed in this paper can be used for quanititative analysis of urban space in visual perception,so as to provide theoretical support and technical means for the construction of the urban space.It is hoped that the attention and discussion on visual quality evaluation of urban space can be aroused.