Time-dependent affine triangulation of spatio-temporal data

Abstract

In the geometric data model [6], spatio-temporal data are modelled as a finite collection of triangles that are transformed by time-dependent affinities. To facilitate querying and animation of spatio-temporal data, we present a normal form for data in the geometric data model. We propose an algorithm for constructing this normal form via a spatio-temporal triangulation of geometric data objects. This algorithm generates new geometric objects that form a partition both in space and in time. A particular property of the proposed partition is that it is invariant under time-dependent affine transformations, and hence independent of the coordinate system chosen when modelling the spatio-temporal data. We can show that our algorithm works correctly and has a polynomial time complexity (in the number of input triangles and the maximal degree of the transformation functions). We also discuss several possible applications of this spatio-temporal triangulation.