Progressive simplification of polygonal curves

Abstract

Simplifying polygonal curves at different levels of detail is an important problem with many applications. Existing geometric optimization algorithms are only capable of minimizing the complexity of a simplified curve for a single level of detail. We present an O(n3m)-time algorithm that takes a polygonal curve of n vertices and produces a set of consistent simplifications for m scales while minimizing the cumulative simplification complexity. This algorithm is compatible with distance measures such as the Hausdorff, the Fréchet and area-based distances, and enables simplification for continuous scaling in O(n5) time. To speed up this algorithm in practice, a technique is presented for efficiently constructing many so-called shortcut graphs under the Hausdorff distance, as well as a representation of the shortcut graph that enables us to find shortest paths in anticipated O(nlog⁡n) time on spatial data, improving over O(n2) time using existing algorithms. Experimental evaluation of these techniques on geospatial data reveals a significant improvement of using shortcut graphs for progressive and non-progressive curve simplification, both in terms of running time and memory usage.