Geographic Elements Selection Algorithm Based on Quadtree in Variable-scale Visualization

Abstract

In order to balance the demand between local and global visualization in the data acquisition, this paper adopts the variable-scale visualization technology and uses quadrangular frustum pyramid projection to show geographic information continuously on a mobile device. In addition, the geographic elements in the variable-scale transition region are crowd because of unceasingly scale changing. In order to solve this problem, this paper presents a quadtree-based geographic elements selection algorithm. That is to say when creating quadtree index, whether node segmentation is needed or not depends on the number of geographic elements which contained in the node space. If the node needs to be segmented, we introduce the selection evaluation function. This algorithm could optimize the display effect and efficiency of variable-scale visualization through abandoning geographic elements based on their evaluation function values. At last, experiments prove that this algorithm could better and faster accomplish variable-scale visualization.