Research On Conflict Resolution Of Map Symbols In Ubiquitous Mapping

The development and compromises of internet technology, smart mobile terminal and wireless messaging technology as well as sensor technology has triggered the curtain on the age of Ubiquitous Mapping. Since ubiquitous mapping is civilian and popular, it requires cartographic process aiming at user requirements and being adapted to the context automatically. As a classic problem of cartography, the conflict resolution of map symbols also needs to adapt to the current ubiquitous mapping development trend which realizes the On-Demand Mapping and the Adaptive Cartography to satisfy the user requirements and the cartography environment. In this paper, a new challenge is presented for the conflict resolution of map symbols in ubiquitous mapping:it not only needs to adjust the map symbols dynamically while taking into account the context, but also needs to synchronously resolve the conflicts of map symbols which occur in the process of adjustment. This thesis researches the conflicts problems of the map symbols appeared in the map rendering process under the ubiquitous mapping background. The primary coverage includes that:1) The background significance of the research on conflict resolution of map symbols in ubiquitous mapping is well explored. It outlines the trend in the separation of data and expression, cartographic environment multiplication and cartographic process popularity in ubiquitous mapping, and points out that the conflict resolution of map symbols ought to meet the user-customizable needs and achieve the real-time context response. Meanwhile, it summarizes domestic and foreign researches in the related topics and concludes the insufficiency from two aspects:one is the different stages of ubiquitous mapping, the other is the constraints of conflict resolution of map symbols.2) The theoretical basis which supports the conflict resolution of map symbols in ubiquitous mapping is systematically expounded, including the conceptual model of the ubiquitous mapping and the conflict resolution of map symbols, the classification system of the context in ubiquitous mapping and its impact on conflict resolution of map symbols, the technical strategy for conflict resolution of map symbols in the complex context environment.3) The characteristics of the POI data, which is the most widely used in the ubiquitous mapping, are analyzed and a method for real-time resolving the conflict of POI symbols is proposed by combining progressive transmission. On the server, the position information of POIs is firstly coded and stored by using Z-Order space-filling curve, then the information of POI's important level is integrated, and lastly spatial index and grade index is constructed by taking this as the basis. The POI set requested by the terminal device thus has level priority and clustered effect in the process of transmission, which suits to the progressive transmission further. On the terminal, the quadtree structure is constructed quickly by using the sequential POI set and then the conflict affected area of currently processing point is determined. At last, POI symbols conflicts in this area is resolved locally to achieve the effect of transmission processing. The experiments indicate that this method realized the On-Demand Mapping and Adaptive Mapping in ubiquitous mapping and got a high quality result.4) To change the symbols of roads and buildings in a different context may bring into conflicts in contemporary web maps. This paper presents a multi-source force field based method to solve this problem, which uses the strategy of co-processing by the server and terminal. On the server, a displacement field is constructed by using the Voronoi diagram and object groups are detected and remained as a whole to retain their spatial patterns and relations. On the terminal, the distance between neighboring polygons in the Voronoi diagram is used to detect conflicts and repulsion sources are introduced in the conflict places. The vectorial sum of each force is computed as the displacement offset distance and direction. At last, distance between neighboring polygons and the displacement offset distance and direction is used to detect and resolve the new conflicts. Taking the displacement of building cluster as the example, this study shows that by using this displacement field model the new conflicts are avoided real-time and spatial relationships of buildings are kept well.5) Label placement is a classic problem of cartography. Based on the analysis of the context environment of the ubiquitous mapping, the strategy of co-processing by the server and terminal is used for label placement and a prompt label placement method is designed, which can satisfy the requirements for customization. On the server, the properties of annotations such as label color, font type and font size are set firstly, then a graph named conflict graph is used to record the conflicts, at last, the genetic algorithm is used to get the placements of each label. On the terminal, the conflict graph is changed while a few annotations'properties is changed with the context, then the connected components of the conflict graph which contains those changed annotations are used to determine which annotations are affected and have to be adjusted, at last, the tabu search algorithm is used to adjust the placements of affected annotations. A set of experiments illustrate that this method for dynamic label placement can meet the real-time demands of various users in ubiquitous mapping.