150 lines
6.4 KiB
Plaintext
150 lines
6.4 KiB
Plaintext
========================================================================
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Copyright 2010, 2011, 2012 Nick Foster
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Quaternion.py copyright 2009 Smithsonian Astrophysical Observatory
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Released under New BSD / 3-Clause BSD License
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All rights reserved
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This file is part of gr-air-modes
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gr-air-modes is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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gr-air-modes is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with gr-air-modes; see the file COPYING. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street,
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Boston, MA 02110-1301, USA.
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========================================================================
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AUTHOR
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Nick Foster <bistromath@gmail.com>
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========================================================================
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OVERVIEW
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gr-air-modes implements a software-defined radio receiver for Mode S
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transponder signals, including ADS-B reports from equipped aircraft.
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Mode S is the transponder protocol used in modern commercial aircraft.
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A Mode S-equipped aircraft replies to radar interrogation by either
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ground radar (secondary surveillance) or other aircraft ("Traffic
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Collision Avoidance System", or TCAS). The protocol is an extended
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version of the Mode A/C protocol used in transponders since the 1940s.
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Mode S reports include a unique airframe identifier (referred to
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as the "ICAO number") and altitude (to facilitate separation control).
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This receiver listens to the 1090MHz downlink channel; interrogation
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requests at 1030MHz are not received or decoded by this program.
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Automatic Dependent Surveillance-Broadcast (ADS-B) is a communication
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protocol using the Extended Mode S transport layer. There are other
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implementations (VDL Mode 2 and UAT, for instance) but Mode S remains
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the primary ADS-B transport for commercial use. The protocol is:
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* Automatic: it requires no pilot input
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* Dependent: it is dependent on altimeter, GPS, and other aircraft
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instrumentation for information
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* Surveillance: it provides current information about the transmitting
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aircraft
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* Broadcast: it is one-way, broadcast to all receivers within range.
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ADS-B-equipped aircraft broadcast ("squitter") their position, velocity,
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flight number, and other interesting information to any receiver within
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range of the aircraft. Position reports are typically generated once per
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second and flight indentification every five seconds.
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Implementation of ADS-B is mandatory in European airspace as well as
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in Australia. North American implementation is still voluntary, with
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a mandate arriving in 2020 via the FAA's "NextGen" program.
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The receiver uhd_modes.py is written for use with Ettus Research USRP
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devices, although the "RTLSDR" receivers are also supported via the
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Osmocom driver. In addition, any receiver which outputs complex
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samples at at least 2Msps should work via the file input or UDP input
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options, or by means of a Gnuradio interface. Multiple output formats
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are supported:
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* Raw (or minimally processed) output of packet data
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* Parsed text
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* SQLite database
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* KML for use with Google Earth
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* SBS-1-compatible output for use with e.g. PlanePlotter or Virtual
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Radar Server
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* FlightGear multiplayer interface for real-time display of traffic
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within the simulator
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Most of the common ADS-B reports are fully decoded per specification.
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Those that are not are generally ones which are not commonly used.
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In particular, should you receive a large number of reports which result
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in "not implemented" or "No handler" messages, please use the -w option
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to save raw data and forward it to the author. To save time, note that
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receiving a small number of spurious reports is expected; false reports
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can be excluded by looking for multiple reports from the same aircraft
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(i.e., the same ICAO 6-digit hexadecimal number).
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========================================================================
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REQUIREMENTS
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gr-air-modes requires:
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* Python >= 2.5 (written for Python 2.7, Python 3.0 might work)
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** NumPy and SciPy are required for the FlightGear output plugin.
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* Gnuradio >= 3.5.0
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* Ettus UHD >= 3.4.0
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* SQLite 3.7 or later
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========================================================================
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USAGE
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The main application is apps/uhd_modes.py. For a complete list of
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options, run:
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$ apps/uhd_modes.py --help
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For use with Ettus UHD-compatible devices, the defaults should suffice
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to receive reports and print to the screen.
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In particular, the --location option should be used to set the receiving
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location's GPS coordinates. This provides better decoding of position
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reports and enables range and bearing calculations.
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========================================================================
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FILES
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Interesting files and libraries included with the package:
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* apps/uhd_modes.py: The main application.
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* apps/get_correlated_records.py: Demonstration program for computing
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multilaterated time error for two unsynchronized receiver stations.
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* lib/air_modes_int_and_dump.cc: Unused integrate-and-dump filter for
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demodulating Mode S waveforms.
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* lib/air_modes_preamble.cc: Mode S preamble detector.
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* lib/air_modes_slicer.cc: Bit slicer (1 vs 0) and packet aggregator.
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* lib/modes_crc.cc: Computes parity check for Mode S packets.
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* python/altitude.py: Mode S altitude encoding/decoding routines
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* python/cpr.py: Compact Position Reporting encoder/decoder
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* python/modes_flightgear.py: FlightGear (open-source flight simulator)
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plugin which inserts live traffic into the simulator via the
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multiplayer interface.
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* python/mlat.py: Multilateration algorithms for determining position of
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non-ADS-B-equipped or non-cooperative aircraft using multiple
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receivers.
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* python/modes_kml.py: KML output plugin for Google Earth.
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* python/modes_parse.py: Mode S/ADS-B packet parsing routines.
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* python/modes_print.py: Human-readable printout plugin
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* python/modes_raw_server.py: UDP output plugin for raw data output
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* python/modes_sbs1.py: SBS-1-compatible output plugin for use with
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Virtual Radar Server, PlanePlotter, or other compatible programs.
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* python/modes_sql.py: SQLite interface for storing reports in a
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database.
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* python/Quaternion.py: Quaternion library used to calculate
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orientation of aircraft for FlightGear plugin.
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