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======================================================================== 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 <firstname.lastname@example.org> ======================================================================== 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: * Automatic: it requires no pilot input * Dependent: it is dependent on altimeter, GPS, and other aircraft instrumentation for information * Surveillance: it provides current information about the transmitting aircraft * Broadcast: it is one-way, broadcast to all receivers within range. 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: * Raw (or minimally processed) output of packet data * Parsed text * SQLite database * KML for use with Google Earth * SBS-1-compatible output for use with e.g. PlanePlotter or Virtual Radar Server * FlightGear multiplayer interface for real-time display of traffic within the simulator 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: * Python >= 2.5 (written for Python 2.7, Python 3.0 might work) ** NumPy and SciPy are required for the FlightGear output plugin. * Gnuradio >= 3.5.0 * Ettus UHD >= 3.4.0 for use with USRPs * osmosdr (any version) for use with RTLSDR dongles * SQLite 3.7 or later * CMake 2.6 or later ======================================================================== 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: * apps/modes_rx: The main application. * apps/get_correlated_records.py: Demonstration program for computing multilaterated time error for two unsynchronized receiver stations. * lib/air_modes_int_and_dump.cc: Unused integrate-and-dump filter for demodulating Mode S waveforms. * lib/air_modes_preamble.cc: Mode S preamble detector. * lib/air_modes_slicer.cc: Bit slicer (1 vs 0) and packet aggregator. * lib/modes_crc.cc: Computes parity check for Mode S packets. * python/altitude.py: Mode S altitude encoding/decoding routines * python/cpr.py: Compact Position Reporting encoder/decoder * python/modes_flightgear.py: FlightGear (open-source flight simulator) plugin which inserts live traffic into the simulator via the multiplayer interface. * python/mlat.py: Multilateration algorithms for determining position of non-ADS-B-equipped or non-cooperative aircraft using multiple receivers. * python/modes_kml.py: KML output plugin for Google Earth. * python/modes_parse.py: Mode S/ADS-B packet parsing routines. * python/modes_print.py: Human-readable printout plugin * python/modes_raw_server.py: UDP output plugin for raw data output * python/modes_sbs1.py: SBS-1-compatible output plugin for use with Virtual Radar Server, PlanePlotter, or other compatible programs. * python/modes_sql.py: SQLite interface for storing reports in a database. * python/Quaternion.py: Quaternion library used to calculate orientation of aircraft for FlightGear plugin.