Urban landmark visuality research based on transfer learning and intelligent pattern recognition:A case study of Nanjing Zifeng Tower
Urban landmark refers to the iconic structures or landscapes in the city,which are the imagery elements in the city with the significance of direction guidance,form unification,value symbolization,historical remembrance and other spatial significance.Cities have paid great attention to the sightline protection and control of landmarks in the hope of highlighting the city's iconic image.Existing research on landmark building sightline protection and control focuses on two directions,one is the method of landmark building sightline protection planning,such as landscape view corridor control,sightline zoning control,fuselage overlook landscape control,etc.,basically adopting the"overlook"method of sightline control,i.e.,a number of viewpoints are selected by the planner or the local government in the city,and it is required that the viewpoints are located at a certain point of view.The planner or local government selects a number of viewpoints in the city,and requires that the landmark buildings can be viewed from the viewpoints without being negatively affected by the neighboring buildings or environmental elements on the overall scene of the landmark buildings.However,the early landmark line of sight analysis is in plan view,delineating the relatively regular sectors and spindle shapes for control,which is more idealized and lacks the refined line of sight simulation analysis.Therefore,with the development of geographic information technology,there is a second major research direction,which is the visual domain simulation analysis of technical methods,such as GIS visual domain analysis,WebGL three-dimensional visual domain analysis,Cesium three-dimensional visual domain analysis,etc.,these methods are from the three-dimensional space to start,through the geographic information data simulation analysis,improve the fineness of the line of sight analysis.However,the method's data quality requirements can't always be fulfilled,according to the current commonly used data accuracy is difficult to meet the demand for visuality analysis,such as building height often can not be obtained directly,often with a floor height of 3 meters projected,such as terrain elevation accuracy of 10 meters as a unit loaded into the system for the remittance of the analysis.In addition,the data of greening,utility poles and other structures are difficult to obtain,as these mentioned above are not loaded into the system such as GIS as an influence factor,resulting in the accuracy of the visuality analysis is limited.Therefore,there is an urgent need for a technology that reflects the visuality of landmark buildings from a real perspective and assists in landmark sightline protection planning and control.Artificial intelligence-based streetscape recognition technology expands the methods of urban environment analysis and provides a new opportunity for landmark visuality analysis.With the advantages of wide coverage,high data refinement,low data collection cost,and intuitive and real scenes,streetscape images have become an important data source for urban environment evaluation research.On the other hand,the continuous breakthroughs in artificial intelligence technology have greatly improved the efficiency of identification and evaluation of urban built environment based on streetscape images on a wide range of spatial scales,and the authenticity and fineness of environmental evaluation have also been improved.However,in general,there is a lack of research on the visuality of specific landmark buildings in streetscape using artificial intelligence,and the main difficulty lies in the accurate identification of specific landmark buildings of different sizes in streetscape images,and the construction of methods and training of models still need to be further explored.On the basis of existing research,this paper proposes a landmark building visuality analysis method based on migration learning and intelligent pattern recognition.Taking the Nanjing landmark building Zifeng Tower as an example,more than 6200 street scene images of Nanjing Gulou District are acquired by panoramic camera,and the GLDv2(Google Landmark Datasets Version 2.0,GLDv2)is utilized to calibrate the size and construct the training set to realize the recognition of different sizes of the Zifeng Tower in each image,and the model learning process is carried out through migration learning method and deep neural network(DNN).The model is loaded into the artificial intelligence body to perform pattern recognition of different sizes of Zifeng Tower appearing in the images,and obtain the visuality of Zifeng Tower on all roads in Gulou District.Compared with traditional geographic information methods such as GIS,street view is closer to the real perspective of individuals,and can provide a real scene of"seeing is believing".Comparative study found that the artificial intelligence analysis method of streetscape images,based on the GIS method,further identifies the influence factors such as greening and structure shading,micro-topography,etc.,and significantly improves the identification accuracy,correcting 40%of the GIS analysis results.Applying the AI analysis results to urban planning and design can identify streets with potential for enhancement and suggest street enhancement for landmark landscape effects.
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