A Seamless and Adaptive LOD Model of the Global Terrain Based on the QTM

Abstract

In this paper, a new seamless and adaptive LOD (Level of Details) modelling method of global terrain based on the QTM (Quaternary Triangular Mesh) is described. Our approach starts with QTM tessellation based on the WGS84 ellipsoidal surface. Thus, the global terrain can be represented by an array of elevation values of QTM vertices. Next, an adaptive idea of a Binary Triangle Tree is inserted in this QTM model to form an adaptive, continuous, and uniform LOD triangular mesh in the DEM grids and their vertices completely coincide with the vertices of QTM. The experiment and analysis are carried out with the global terrain data, GTOPO30. The results illustrate that: (1) the global DEM model based on QTM is seamless, hierarchical, and regular over the whole Earth, and the dataset occupies only about half of its initial size; (2) an adaptive LOD (Level of Details) model of the DEM data blocks is constructed and the problem of discontinuity in different subdivision levels is overcome; and (3) the number of the triangles in this adaptive LOD model decreases greatly as their error tolerances increase, but there is no obvious change in the results