In the 1960s and 1970s, the first wave of ITS-developed computer programs for propagation prediction was published. Perhaps the most famous and influential was Anita G. Longley and Philip L. Rice's "Prediction of Tropospheric Radio Transmission Loss Over Irregular Terrain: A Computer Method - 1968," NTIA Technical Report ERL 79-ITS 67, July 1968. The technical report provided the mathematical algorithms, flow charts, and logic used to develop the code, and the FORTRAN code was printed out in an Annex. The Longley-Rice model, which is more commonly referred to as the Irregular Terrain Model or ITM, is a general purpose model that can be applied to a large variety of engineering problems to predict propagation for radio frequencies between 20 MHz and 20 GHz, and is still in widespread use today. Since that time, ITS has continued to develop and refine computer programs for propagation prediction based on electromagnetic theory and on statistical analyses of both terrain features and radio measurements. The iterative cycle of modeling and measurement, with constant reference to first principles, produced models that are highly regarded. At the beginning of the 21st Century, ITS embarked on a systematic program of updating these software implementations. Today, ITS publishes open-source propagation model software implementations at the NTIA GitHub Repository. There, too, ITS provides other open-source software tools used in our research. The ITS Open Source Software list provides direct links to individual repositories.
Below are links to information and downloads for some of the most durable legacy ITS propagation model software implementations. The FORTRAN implementations are no longer maintained, but may be useful for research purposes.
High Frequency (HF) Propagation Models (2-30 MHz)
Irregular Terrain Model (ITM) (Longley-Rice) (20 MHz - 20 GHz)
IF-77 Wave Propagation Model (Gierhart-Johnson) (Air-Ground)
- Millimeter-wave Propagation Model (MPM) (1 GHz - 1 THz)
Terrain Data and Extraction Routines