======================================================================== Copyright 2010, 2011, 2012 Nick Foster
Quaternion.py copyright 2009 Smithsonian Astrophysical Observatory Released under New BSD / 3-Clause BSD License All rights reserved
This file is part of gr-air-modes
gr-air-modes is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.
gr-air-modes is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with gr-air-modes; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Boston, MA 02110-1301, USA.
======================================================================== AUTHOR
Nick Foster bistromath@gmail.com
======================================================================== OVERVIEW
gr-air-modes implements a software-defined radio receiver for Mode S transponder signals, including ADS-B reports from equipped aircraft.
Mode S is the transponder protocol used in modern commercial aircraft. A Mode S-equipped aircraft replies to radar interrogation by either ground radar (secondary surveillance) or other aircraft ("Traffic Collision Avoidance System", or TCAS). The protocol is an extended version of the Mode A/C protocol used in transponders since the 1940s. Mode S reports include a unique airframe identifier (referred to as the "ICAO number") and altitude (to facilitate separation control). This receiver listens to the 1090MHz downlink channel; interrogation requests at 1030MHz are not received or decoded by this program.
Automatic Dependent Surveillance-Broadcast (ADS-B) is a communication protocol using the Extended Squitter capability of the Mode S transport layer. There are other implementations (VDL Mode 2 and UAT, for instance) but Mode S remains the primary ADS-B transport for commercial use. The protocol is:
ADS-B-equipped aircraft broadcast ("squitter") their position, velocity, flight number, and other interesting information to any receiver within range of the aircraft. Position reports are typically generated once per second and flight indentification every five seconds.
Implementation of ADS-B is mandatory in European airspace as well as in Australia. North American implementation is still voluntary, with a mandate arriving in 2020 via the FAA's "NextGen" program.
The receiver modes_rx is written for use with Ettus Research USRP devices, although the "RTLSDR" receivers are also supported via the Osmocom driver. In theory, any receiver which outputs complex samples at at least 2Msps should work via the file input or UDP input options, or by means of a Gnuradio interface. Multiple output formats are supported:
Most of the common ADS-B reports are fully decoded per specification. Those that are not are generally ones which are not commonly used.
Should you receive a large number of reports which result in "not implemented" or "No handler" messages, please use the -w option to save raw data and forward it to the author. To save time, note that receiving a small number of spurious reports is expected; false reports can be excluded by looking for multiple reports from the same aircraft (i.e., the same ICAO 6-digit hexadecimal number).
======================================================================== REQUIREMENTS
gr-air-modes requires:
======================================================================== BUILDING
gr-air-modes uses CMake as its build system. To build, from the top level directory, type:
$ mkdir build $ cd build $ cmake ../ $ make $ sudo make install $ sudo ldconfig
This will build gr-air-modes out of the source tree in build/ and install it on your system, generally in /usr/local/bin.
======================================================================== USAGE
The main application is modes_rx. For a complete list of options, run:
$ modes_rx --help
For use with Ettus UHD-compatible devices, the defaults should suffice to receive reports and print to the screen. Use the -d option to look for an RTLSDR-type dongle using the osmosdr driver.
In particular, the --location option can be used to set the receiving location's GPS coordinates. This enables range and bearing calculations in the printed display as well as range rings in the Google Earth interface.
======================================================================== FILES
Interesting files and libraries included with the package: