Comprehensive Study, No Grade Scale Of Gis-based Urban Road

Dynamic scale map generalization is a technique that enables GIS output spatial data size increasing or reducing automatically in accordance with the map scale. Using a large scale spatial database as the foundation, it makes the capacity of spatial data adapts to the map scale automatically.As GIS developing, the demand of maps of different scales is increasing dramatically. However, the technique of automatic map generalization is not so good to realize the automatization of map generalization. So map generalization today is still relying on manual work. This situation can't meet the request of the developing society at all. Thus, study on dynamic scale map generalization is pretty important.Linear feature is an important part of the map database, so line generalization greatly shows the capability of map generalization systems. Existing map generalization systems are short of non-spacial feature and seldom take region geographic character into account. Moreover, Most of them ignore the integration of map generalization and GIS. On researching answerof these problems, this paper proposes innovation as follow:First, according to the need of automatic map generalization and the character of urban roads, the paper summarizes ways of road classification in classic map generalization and other areas, and proposes a way to classify urban roads, which is suitable for automatic map generalization.Second, integrate GIS technology into map generalization. In this paper, using special analyse function of GIS, we query special relationships between different features. The querying result is used as important feature data of importance estimate of urban roads.Third, at present, automatic map generalization ignores region geographic character a lot. Aimed at this problem, the paper improves the urban road importance estimate system in Yin's map generalization theory, including rationalization of the selection of estimate indexes and divides the region into some sub-areas according to road density.Fourth, according to the urban road importance estimate system and the character of the city, with feature-oriented idea, the paper designs a hierarchy structured database for urban road generalization.Fifth, after researching, this paper chooses complex exponent and extraction model of dynamic scale theory as the quantity selection model.The author choose Beijing urban area as the study region.Using MS Visual Basic 6.0 and MapObjects by ESRI, the paper designs a dynamic scale map generalization system of...