Generalizing Simultaneously to Support Smooth Zooming: Case Study of Merging Area Objects

Dongliang Peng, Martijn Meijers*, Peter van Oosterom

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

19 Downloads (Pure)


When users zoom in or out on a digital map, the map should change correspondingly to present geographical information at proper levels. A way to help map users better keep track of their interested objects is to change the map smoothly instead of discretely switching between several levels of detail. This paper focuses on the problem of providing smooth merging of area objects. We propose to merge multiple areas simultaneously to share their animation durations. In this way, each merging operation can be prolonged, and it is visually smoother. We present a greedy algorithm to decide which areas should be merged at each step. The merging process is pre-computed and is recorded into a space-scale cube (SSC). When a user accesses our web map, the SSC is sent to the client side so that the map can be generated by slicing the SSC in the graphics processing unit (GPU). We also explain how to snap the zooming to valid states so that the zooming will not stop halfway of the merging operations. Our case study shows that it is visually smoother to merge simultaneously than to sequentially merge each pair of areas.

Original languageEnglish
Article number12
Number of pages19
JournalJournal of Geovisualization and Spatial Analysis
Issue number1
Publication statusPublished - 2023


  • Continuous map generalization
  • Simultaneous generalization
  • Space-scale cube
  • Vario-scale map
  • Web map

Cite this