Digital terrain database structures and accuracy requirements for propagation modelling

Digital terrain elevation model (DTEM) databases are essential for realistically calculating path loss and coverage areas for radio communication systems of all types. Because such propagation models are well-suited to computer programs, the factors determining efficient DTEM data structure and necessary DTEM data accuracy are largely derived from the requirements of the computerized propagation models. The author discusses DTEM data structures for efficient elevation retrieval, and examines the required DTEM accuracy needed to achieve acceptable path loss results given commonly-used diffraction loss propagation primitives. The results show that obstacle elevation errors of the order of 15-25 meters can be tolerated before calculated path loss changes by more than about 2 dB on obstructed paths