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
wh_whd@sohu.com
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.