Genetic Algorithems Study In Urban Spatial Growth Quantificational Methods

With the development of society and economy, cities, the main space that human inhabit, also develop and change. In order to improve the life quality and life environment, people attack more and more importance to urban planning and management. The main goal of urban planning and management is to advance development of urban space harmoniously and improve space environment. Obviously, the urban planning is the precondition and the base of urban land development and urban construction. So the level of urban planning will affect the development degree of urban. The analysis of urban spatial growth is the important foundation and one part of urban planning. The aim of this paper is to aid urban spatial growth analysis by the realization of UG-GA model. In order to finish the UG-GA model, the follow works should be done. 1. study background for UG-GA model 1) study for digital urban planning systemWith development of science, technology and information technology, in order to increase the level of urban planning and make urban planning more objective and scientific, people will enhance the methods by using electron and computer technique. Now, the application of information technique in urban planning bring benefit for the job of urban planning and management enormously, and go into the every step of job for urban planning and management, and become the essential part of urban planning and management. This builds a digital urban planning system. Urban planning is the induce, analysis, deduce and prediction by the history data and present conditions. People hope that they can insight the urban development law and find the nature of urban development by the surface of urban. So the urban planning is the most necessary field for exploring the methods of GIS application,especially when the data mining method and theory , which bring the enlightenment for GIS application in urban planning, was put forward. Through the digital urban planning system, We can find that the GIS application in the urban planning analysis if the other study direction in this field, and urban spatial growth analysis is the important study direction of urban planning analysis.2) The viable quantitative analysis of system engineering combined with GISBecause the level of urbanization is not high, the urban space increase is a long and unavoidable process. It refers to the field of urban society, economy, political, geography, etc, and is the basis the urban spacial planning. So the analysis of urban spacial growth own the important significance for urban planning. The urban space growth is a complex process. Because of its complexity, it is always analyzed qualitatively. But the quantitative analysis is one important method, which can represent the big-small, more-less, strong-weak, increasing-decreasing more clearly. Although system engineer theory supply the basis methods for quantitative analysis, but be lack of support of spatial location. It is difficult to finish space analysis and representation, that GIS supply very well. If it is combined with quantitative methods and math model, we will get more valuable information than simply qualitative analysis. This paper will represent the spatial developing process by the GA and relate space technique, that explore more expansive urban spacial analysis field, and provide help for the working-out of urban planning.3) The suitable analysis of GA application in urban spatial growthGA is a kind of self-adaptive technique that simulate the evolution of nature biology for acquiring best answer, which just accord with the characteristic in urban spatial growth process, such as land fitting together optimally , andexisting multi-spatial-possibilities for different demands. GA operate well and simply, which is helpful for realization of model.2. The foundation theory study for UG-GA model1) The mechanism and pattern study for urban spatial growthThe point that this paper emphasize particularly on is the quantitative methods, which is the foundation of model. Quantitative process must be finished by understanding urban developing mechanism and the qualitative analysis of factors that affect the space growth. So firstly, the paper gives the urban expanding mechanism and the urban growth basis motivity. The urban growth mode, such as expanding along road line, expanding gradually, expanding bouncingly, are the outcome of different dynamic factors. All the factors represent on the aspects of ecology competition, society, market, policy, etc and all kind of urban development conditions, they affect and control the urban growth mode, pattern, and direction. So we need master the urban present growth pattern, and combine them with urban spatial growth mechanism, for exploring the basis dynamic about pattern forming.2) The study on spatial data foundation in urban planningThe above factors are all belong to some space location. So in cording to finishing the calculation, we should consider how to represent these factors and conditions under the digital mode and how operate on them. Urban planning and urban spatial growth analysis need many kinds of data, which have its own characteristic. According to the demand of urban planning and the foundation of urban GIS, the data are divided into three level, that is basis level, entity level, and structure level, urban planning analysis and operate need the support of the three level data. In addition, because urban spatial growth process consists of individual parcel evolvement and the parcels relations evolvement, and it need data mining technique and measure methods to get these relationpattern, the paper give the form of urban land evolvement, spacial data mining methods for pattern analysis, the spacial measure method and the process for it. 3) The study on basis theory and realization methods of GA GA is a relative mature algorithm, and include many method and algorithm. In order to select suitable algorithm, we should compare present GA technique and methods, and select good and viable methods, which establish firm base for UA-GA model. "3. The realization theory study for UA-GA model1) The realization frame studyThe basis frame of UG-GA model include the basis coverage and factor coverage. On the representation of basis coverage, it can make use of comprehensive planning and detail planning, and other represented mode, such as regulative different precise parcel. For the determining of factors coverage, the factors that affect the urban spatial growth are dealt with, and put into factors database, as spatial factor coverage that will be used at any moment.2) The study on the urban spatial growth forceThe factors and conditions that affect urban spatial growth exist in various fields of society and economy, and produce different effect for land use. According to the different effect, these factors are abstracted as centripetal force, centrifugal force, gravitation, resistance, and friction for area development, which will support the quantitative process of factors.3) The study on quantitative methods and process of urban spatial growth forceCombined with the characteristic of these force, under the support of GIS spatial analysis methods and system engineer, the factor quantitative method and calculating process of force are given.4) Study about GA application method and process in urban spatialgrowth analysisGA is a algorithm that imitate biology, which accords with the process of continuous adjustment and improvement of urban in urban development. The factors that affect urban growth are complex, the objective condition provide the foundation and environment for natural evolvement, and subjective control can produce the variation that will damage the pattern of urban development and bring new pattern of growth. Combined with the characteristics of urban planning and the theory of urban space growth, we will determined the GA process that suits for urban space grow analysis and includes the determining of code, suitable degree function, beginning cluster, selecting arithmetic operators, across arithmetic operators and relate parameter, etc. Finally, we practice UG-GA model on the WuHan city.4. Conclusion of UG-GA model practiceThis paper explores the new fields about new technique and methods application in urban planning, and combine the space analysis with GA together, that exert the potential power of math model and quantitative, qualitative analysis methods. Because some limit factors , the model still have developed room. In this paper, the advantages, disadvantages and present limited factors are summarized, and some advancing methods and development directions are given. The UG-GA model will be further improved by later efforts.