Abstract
Scale reduction from source to target maps inevitably leads to conflicts of map symbols in cartography and geographic information systems (GIS). Displacement is one of the most important map generalization operators and it can be used to resolve the problems that arise from conflict among two or more map objects. In this paper, we propose a combined approach based on constraint Delaunay triangulation (CDT) skeleton and improved elastic beam algorithm for automated building displacement. In this approach, map data sets are first partitioned. Then the displacement operation is conducted in each partition as a cyclic and iterative process of conflict detection and resolution. In the iteration, the skeleton of the gap spaces is extracted using CDT. It then serves as an enhanced data model to detect conflicts and construct the proximity graph. Then, the proximity graph is adjusted using local grouping information. Under the action of forces derived from the detected conflicts, the proximity graph is deformed using the improved elastic beam algorithm. In this way, buildings are displaced to find an optimal compromise between related cartographic constraints. To validate this approach, two topographic map data sets (i.e., urban and suburban areas) were tested. The results were reasonable with respect to each constraint when the density of the map was not extremely high. In summary, the improvements include (1) an automated parameter-setting method for elastic beams, (2) explicit enforcement regarding the positional accuracy constraint, added by introducing drag forces, (3) preservation of local building groups through displacement over an adjusted proximity graph, and (4) an iterative strategy that is more likely to resolve the proximity conflicts than the one used in the existing elastic beam algorithm.
Highlights
Map generalization is an abstraction process that aims to represent geographic information according to the scale and purpose of the map [1, 2]
The proposed approach was implemented in a testing generalization platform that had been developed based on the ArcGIS Engine developer kit
This study proposes a combined approach to automated building displacement in map generalization
Summary
Map generalization is an abstraction process that aims to represent geographic information according to the scale and purpose of the map [1, 2]. Scale reduction from source to target maps inevitably leads to conflicts in map symbols, in which map objects overlap or become too dense to be clearly distinguished [4]. To remove these conflicts, several generalization operators should be used, such as displacement, deletion, exaggeration, aggregation, and typification [5]. Several generalization operators should be used, such as displacement, deletion, exaggeration, aggregation, and typification [5] Among these operators, displacement is one of the most important contextual operators used to resolve the problems that arise among two or more conflicting map objects. Finding better automated displacement approaches to automated map generalization is necessary
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