This code repository archives the FORTRAN and C++ ITS Irregular Terrain Model (ITM) version 1.2.2. ITM predicts terrestrial radiowave propagation for frequencies between 20 MHz and 20 GHz based on electromagnetic theory and empirical models developed by Anita Longley and Phil Rice. Propagation mechanisms considered include free space loss, diffraction, and troposcatter. Specifically, ITM predicts attenuation as a function of distance (greater than 1 km), terminal heights, meteorological conditions, terrain effects, and the variability of the signal in time and in space.
The FORTRAN and C++ implementations of ITM are both version 1.2.2 and are maintained here for historical purposes. A new C++ implementation of ITM has been established here. This new C++ implementation, initially designated version 1.3, is functionally identical to the archived v1.2.2 software. The new C++ code base is where all future updates and improvements to ITM will be applied and versioned.
A list and short description of all files part of the software release can be viewed here.
- G.A. Hufford, A.G. Longley, W.A. Kissick, A Guide to the Use of the ITS Irregular Terrain Model in the Area Prediction Mode, NTIA Technical Report TR-82-100, April 1982.
- G.A. Hufford, The ITS Irregular Terrain Model, version 1.2.2 Algorithm.
- G.A. Hufford, 1985 ITM Memo, Dr. George Hufford's 1985 Memo describing the changes to ITM version 1.2.1 (dated April, 1979) in ITM version 1.2.2 (dated September, 1984)
- G.A. Hufford, The Irregular Terrain Model, The "definitive" representation of the ITS Irregular Terrain Model. It contains both the source code and a rather extensive documentation.
- A.G. Longley and P.L. Rice, Prediction of Tropospheric Radio Transmission Loss Over Irregular Terrain: A Computer Method - 1968, NTIA Technical Report ERL 79-ITS 67, July 1968.
For technical questions about ITM, contact Paul McKenna, (303) 497-3474, pmckenna@ntia.gov.