Linearized terrain: Languages for silhouette representations

Abstract

The scope of this paper is a qualitative description of terrain features that can be characterized using the silhouette of a terrain. The silhouette is a profile of a landform seen from a particular observer's perspective. We develop a terrain language as a formal framework to capture terrain features. The horizon of a terrain silhouette is represented as a string. The alphabet of the terrain language comprises straight-line segments. These line primitives are classified according to three criteria: (1) the alignment of their slope, (2) their relative lengths, characterized by orders of magnitude, and (3) their differences in elevation, described by an order relation. We employ term rewritin..