A hierarchical model for approximating 2-1/2-dimensional surfaces is described. This model, called a Delaunay pyramid, is a method for compression of spatial data and representation of a surface at successively finer levels of detail. A Delaunay pyramid is based on a sequence of Delaunay triangulations of suitably defined subsets of the set of data points. A triangle-oriented encoding structure for a Delaunay pyramid is presented, and its storage complexity is evaluated. An algorithm for constructing a Delaunay pyramid is described, and a method for solving the point location and evaluation on such a model is discussed