¹Pacific Northwest National Laboratory, Washington State University, U.S.A.

Correspondence: Kevin Mote, Pacific Northwest National Laboratory, Washington State University, U.S.A. E-mail: Kevin.Mole@pnl.gov

Received 19 June 2007; Revised 28 September 2007; Accepted 10 February 2007.

Abstract

This paper describes a fast approach to automatic point label de-confliction on interactive maps. The general Map Labeling problem is NP-hard and has been the subject of much study for decades. Computerized maps have introduced interactive zooming and panning, which has intensified the problem. Providing dynamic labels for such maps typically requires a time-consuming pre-processing phase. In the realm of visual analytics, however, the labeling of interactive maps is further complicated by the use of massive datasets laid out in arbitrary configurations, thus rendering reliance on a pre-processing phase untenable. This paper offers a method for labeling point-features on dynamic maps in real time without pre-processing. The algorithm presented is efficient, scalable, and exceptionally fast; it can label interactive charts and diagrams at speeds of multiple frames per second on maps with tens of thousands of nodes. To accomplish this, the algorithm employs a novel geometric de-confliction approach, the 'trellis strategy,' along with a unique label candidate cost analysis to determine the 'least expensive' label configuration. The speed and scalability of this approach make it well-suited for visual analytic applications.