U.S. Department of Commerce NTIA/ITS
Institute for Telecommunication Sciences
Irregular Terrain Model (ITM) (Longley-Rice)
Abstract:
The ITS model of radio propagation for frequencies between 20 MHz
and 20 GHz (the Longley-Rice model) (named for Anita Longley & Phil Rice, 1968)
is a general purpose model that
can be applied to a large variety of engineering problems. The model,
which is based on electromagnetic theory and on statistical analyses of
both terrain features and radio measurements, predicts the median
attenuation of a radio signal as a function of distance and the
variability of the signal in time and in space.
Disclaimer:
The software contained within was developed by an agency of the
U.S. Government. NTIA/ITS has no objection to the use of this
software for any purpose since it is not subject to copyright
protection in the U.S.
No warranty, expressed or implied, is made by NTIA/ITS or the
U.S. Government as to the accuracy, suitability and functioning of
the program and related material, nor shall the fact of
distribution constitute any endorsement by the U.S. Government.
Description of the ITM/Longley-Rice model
Adobe Acrobat formatted files (.pdf):
- itm_alg.pdf
- The ITS Irregular Terrain Model, version 1.2.2 Algorithm.
- itm.pdf
- The "definitive" representation of the ITS Irregular
Terrain Model. It contains both the source code and
a rather extensive documentation.
Updated 5 Aug 2002 to fix missing functions (TeX to pdf conversion problem).
TeX formatted files (.tex)
(If unfamiliar with TeX, use the .pdf files above):
- itm_alg.tex
- The ITS Irregular Terrain Model, version 1.2.2 Algorithm,
written in the TeX language.
It is a stand-alone file, prepared for Plain TeX.
It might be almost readable as is.
- itm.tex
itm.cts
itm.mds
itm.ndx
fwebmac.sty
- The documentation files for the programming of the ITM.
This is written in the TeX language and should have the program
TEX applied to it. As is it is not very readable.
FORTRAN source code and sample results:
- itm.for
- The source code for the ITM subroutines.
- itm_man.txt
- A manual for ITM. A straight ASCII file intended to
aid the programmer in preparing a main program that
involves the ITM.
- uarea.for
- "User's Area model," to illustrate one way to use the
ITM in the area prediction mode.
It is interactive with output directed to a file of the user's choice.
This is the source code for the main program.
- uarea.exe
- An executable file for UAREA. Runs on a PC under DOS.
- uarea_man.txt
- A manual for UAREA. A straight ASCII file.
- qkpfl.for
- "Quick Profile," to illustrate one way to use the ITM
in the point-to-point mode.
It was written for batch processing on a main frame computer,
but may be run on a PC by redirecting input and output.
This is the source code for the main program.
- qkpflman.txt
- A manual for QKPFL. A straight ASCII file.
- qkpfl.exe
- An executable file for QKPFL. Runs on a PC under DOS.
- qkpfl32.exe
- An executable file for QKPFL. Runs on a PC under DOS (in 32-bit mode).
- You will need to put salflibc.dll
into your C:\WINDOWS\SYSTEM directory for it to work.
- qkpflbat.txt
qkpfldat.txt
qkpflanx.txt
- A sample showing how to run QKPFL on a PC--a batch file
which runs the program using QKPFL.DAT as input and
writing output to QKPFL.ANS. When run, the latter may
be compared with QKPFL.ANX.
Files should be renamed to QKPFL.BAT, QKPFL.DAT, and QKPFL.ANX.
The .txt suffix was used to easily view the files with your browser.
C++ source code is now available:
- ITMDLL.cpp
(Updated 06/26/07)
- ITMsetup.exe
- An executable file for ITM (C++ version) using the GLOBE terrain database
(You must download this separately).
- To see more information about GLOBE, see our
GLOBE extraction routines.
- Runs on a PC under Windows.
- Some documentdation is in Word format. If you do not have Word,
you can install this
Word viewer.
- For questions with the C++ code, contact NTIA/OSM for support: