Published online by Cambridge University Press: 04 July 2016
This paper describes the use of oct-trees to representdigitised terrain elevation data (DTED) in terrainreference navigation (TRN) systems. Oct-treesprovide a regular method to represent digitisedterrain data where the level of detail of theterrain is encoded in the tree structure. The use ofoct-trees also provides a basis for a significantreduction in the on-line storage requirement forDT-EDs. A method of encoding using Morton orderingis introduced which allows DTEDs to be accessed asoct-trees and quad-trees where the tree structuresare represented as pointerless structures.Algorithms to construct and access terrain oct-treesare presented which form a set of access primitivesfor tree operations required in TRN applications.The paper concludes with examples to illustrate theefficiency of the methods described in the paper fortwo DTEDs, in terms of performance of the treeaccess operations and reductions in storage.