RESEARCH ON AUTOMATED ROUTE SCHEMATIC MAP GENERALIZATION IN MOBILE ENVIRONMENT
W. Dong1, J. Liu2, Q. Guo3
1 - School of Resource and Environment Science, Wuhan University, Wuhan, China; Chinese Academy of Surveying and Mapping, Beijing, China
2 - Chinese Academy of Surveying and Mapping, Beijing, China
3 - School of Resource and Environment Science,Wuhan University, Wuhan, China
With the wireless mobile environment grows and the variety of the contents increases, more and more information services which have the same quality in wired internet services are desired. One of them is the map service. The mobile phone's portability allows the map services to have higher potentiality of growth. Because of the restrictions of memory, process and screen size, it is difficult to represent information in a mobile phone. Therefore, it is very important to research cognitive characteristics of map symbols and to research how to design and offer simplified and clarified map adapted to mobile equipment. Schematic map is a quit effective, efficient and satisfied map form for mobile map services.
In cartography, graphic schematization is one aspect of map generalization. Map generalization offers a function for reducing map data and reducing density of objects for increasing human ability of understanding the map. To represent the map data on a small screen like a mobile phone, we research the cartographical principles of schematic map are as follows(J. Mark Ware,2006).①Topological-original network and derived schematic map should be topologically consistent;②Orientation-if possible, network edges should lie in horizontal, vertical or diagonal direction;③Length-if possible, all network edges should have length greater than some minimum length (in order to reduce congestion);④Angle-if possible, the angle between a pair of connected edges should be greater than some minimum angle;⑤Rotation-an edge’s orientation should remain as close to its starting orientation as possible;⑥Clearance-if possible, the distance between disjoint features should be greater than some minimum distance;⑦Displacement-vertices should remain as close to their starting positions as possible.
Based on these principles, we set score functions and adopt a new map generalization method to design the schematic map. Firstly, according to the impact of a vertex on the shape of the line to which it belongs, we divide these points into three types—fix points, movable points and removable points. Then we simplify the route line segments by progressive selection of route points while inspecting the topological consistency of route network. Secondly we progressively adjust and iteratively compute line segments direction according to the horizontal, vertical or diagonal constrained by schematic map constrains. Finally we turn the detailed map into a well understandable schematic map on small screens and maintain the route network topological consistency by designing an experimentation system.