4ecd6958a1
This is possible now that the SBS output doesn't rely on the global block timestamp; the output will look like this: MSG,8,111,11111,4AC954,111111,2015/02/08,17:57:53.917,2015/02/08,17:57:53.936,,,,,,,,,,,,0 MSG,7,111,11111,392AEB,111111,2015/02/08,17:57:53.744,2015/02/08,17:57:53.936,,15375,,,,,,,,,,0 MSG,8,111,11111,392AEB,111111,2015/02/08,17:57:53.917,2015/02/08,17:57:53.936,,,,,,,,,,,,0 MSG,6,111,11111,800387,111111,2015/02/08,17:57:53.919,2015/02/08,17:57:53.936,,,,,,,,4745,0,0,0,0 where the "receive timestamp" (first time column) goes backwards to reflect the original reception time of the delayed message, but the "forwarded timestamp" (second time column) reflects the actual forwarding time.
523 lines
20 KiB
C
523 lines
20 KiB
C
// Part of dump1090, a Mode S message decoder for RTLSDR devices.
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//
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// track.c: aircraft state tracking
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//
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// Copyright (c) 2014,2015 Oliver Jowett <oliver@mutability.co.uk>
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//
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// This file is free software: you may copy, redistribute and/or modify it
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// under the terms of the GNU General Public License as published by the
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// Free Software Foundation, either version 2 of the License, or (at your
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// option) any later version.
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//
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// This file is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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// This file incorporates work covered by the following copyright and
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// permission notice:
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//
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// Copyright (C) 2012 by Salvatore Sanfilippo <antirez@gmail.com>
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//
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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//
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// * Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include "dump1090.h"
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//
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// Return a new aircraft structure for the linked list of tracked
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// aircraft
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//
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struct aircraft *trackCreateAircraft(struct modesMessage *mm) {
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static struct aircraft zeroAircraft;
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struct aircraft *a = (struct aircraft *) malloc(sizeof(*a));
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int i;
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// Default everything to zero/NULL
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*a = zeroAircraft;
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// Now initialise things that should not be 0/NULL to their defaults
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a->addr = mm->addr;
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for (i = 0; i < 8; ++i)
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a->signalLevel[i] = mm->signalLevel; // First time, initialise everything
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// to the first signal strength
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// mm->msgtype 32 is used to represent Mode A/C. These values can never change, so
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// set them once here during initialisation, and don't bother to set them every
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// time this ModeA/C is received again in the future
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if (mm->msgtype == 32) {
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int modeC = ModeAToModeC(mm->modeA | mm->fs);
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a->modeACflags = MODEAC_MSG_FLAG;
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if (modeC < -12) {
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a->modeACflags |= MODEAC_MSG_MODEA_ONLY;
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} else {
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mm->altitude = modeC * 100;
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mm->bFlags |= MODES_ACFLAGS_ALTITUDE_VALID;
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}
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}
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// Copy the first message so we can emit it later when a second message arrives.
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a->first_message = *mm;
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return (a);
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}
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//
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//=========================================================================
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//
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// Return the aircraft with the specified address, or NULL if no aircraft
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// exists with this address.
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//
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struct aircraft *trackFindAircraft(uint32_t addr) {
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struct aircraft *a = Modes.aircrafts;
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while(a) {
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if (a->addr == addr) return (a);
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a = a->next;
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}
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return (NULL);
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}
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//
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// CPR position updating
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//
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// Distance between points on a spherical earth.
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// This has up to 0.5% error because the earth isn't actually spherical
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// (but we don't use it in situations where that matters)
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static double greatcircle(double lat0, double lon0, double lat1, double lon1)
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{
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lat0 = lat0 * M_PI / 180.0;
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lon0 = lon0 * M_PI / 180.0;
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lat1 = lat1 * M_PI / 180.0;
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lon1 = lon1 * M_PI / 180.0;
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return 6371e3 * acos(sin(lat0) * sin(lat1) + cos(lat0) * cos(lat1) * cos(fabs(lon0 - lon1)));
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}
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static int doGlobalCPR(struct aircraft *a, int fflag, int surface)
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{
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int result;
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double lat=0, lon=0;
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if (surface) {
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// surface global CPR
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// find reference location
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double reflat, reflon;
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if (a->bFlags & MODES_ACFLAGS_LATLON_REL_OK) { // Ok to try aircraft relative first
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reflat = a->lat;
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reflon = a->lon;
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} else if (Modes.bUserFlags & MODES_USER_LATLON_VALID) {
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reflat = Modes.fUserLat;
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reflon = Modes.fUserLon;
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} else {
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// No local reference, give up
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return (-1);
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}
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result = decodeCPRsurface(reflat, reflon,
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a->even_cprlat, a->even_cprlon,
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a->odd_cprlat, a->odd_cprlon,
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fflag,
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&lat, &lon);
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} else {
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// airborne global CPR
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result = decodeCPRairborne(a->even_cprlat, a->even_cprlon,
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a->odd_cprlat, a->odd_cprlon,
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fflag,
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&lat, &lon);
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}
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if (result < 0)
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return result;
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// check max range
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if (Modes.maxRange > 0 && (Modes.bUserFlags & MODES_USER_LATLON_VALID)) {
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double range = greatcircle(Modes.fUserLat, Modes.fUserLon, lat, lon);
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if (range > Modes.maxRange)
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return (-2); // we consider an out-of-range value to be bad data
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}
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a->lat = lat;
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a->lon = lon;
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return 0;
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}
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static int doLocalCPR(struct aircraft *a, int fflag, int surface, time_t now)
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{
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// relative CPR
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// find reference location
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double reflat, reflon, lat=0, lon=0;
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double range_limit = 0;
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int result;
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if (a->bFlags & MODES_ACFLAGS_LATLON_REL_OK) {
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int elapsed = (int)(now - a->seenLatLon);
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if (elapsed < 0) elapsed = 0;
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reflat = a->lat;
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reflon = a->lon;
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// impose a range limit based on 2000km/h speed
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range_limit = 5e3 + (2000e3 * elapsed / 3600); // 5km + 2000km/h
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} else if (!surface && (Modes.bUserFlags & MODES_USER_LATLON_VALID)) {
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reflat = Modes.fUserLat;
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reflon = Modes.fUserLon;
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// The cell size is at least 360NM, giving a nominal
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// max range of 180NM (half a cell).
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//
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// If the receiver range is more than half a cell
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// then we must limit this range further to avoid
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// ambiguity. (e.g. if we receive a position report
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// at 200NM distance, this may resolve to a position
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// at (200-360) = 160NM in the wrong direction)
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if (Modes.maxRange > 1852*180)
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range_limit = (1852*360) - Modes.maxRange;
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} else {
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// No local reference, give up
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return (-1);
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}
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result = decodeCPRrelative(reflat, reflon,
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fflag ? a->odd_cprlat : a->even_cprlat,
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fflag ? a->odd_cprlon : a->even_cprlon,
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fflag, surface,
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&lat, &lon);
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if (result < 0)
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return result;
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// check range limit
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if (range_limit > 0) {
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double range = greatcircle(reflat, reflon, lat, lon);
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if (range > range_limit)
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return (-1);
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}
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// check max range
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if (Modes.maxRange > 0 && (Modes.bUserFlags & MODES_USER_LATLON_VALID)) {
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double range = greatcircle(Modes.fUserLat, Modes.fUserLon, lat, lon);
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if (range > Modes.maxRange)
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return (-2); // we consider an out-of-range value to be bad data
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}
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a->lat = lat;
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a->lon = lon;
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return 0;
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}
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static void updatePosition(struct aircraft *a, struct modesMessage *mm, time_t now)
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{
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int location_result = -1;
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if (mm->bFlags & MODES_ACFLAGS_LLODD_VALID) {
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a->odd_cprlat = mm->raw_latitude;
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a->odd_cprlon = mm->raw_longitude;
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a->odd_cprtime = mstime();
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} else {
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a->even_cprlat = mm->raw_latitude;
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a->even_cprlon = mm->raw_longitude;
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a->even_cprtime = mstime();
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}
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// If we have enough recent data, try global CPR
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if (((mm->bFlags | a->bFlags) & MODES_ACFLAGS_LLEITHER_VALID) == MODES_ACFLAGS_LLBOTH_VALID && abs((int)(a->even_cprtime - a->odd_cprtime)) <= 10000) {
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location_result = doGlobalCPR(a, (mm->bFlags & MODES_ACFLAGS_LLODD_VALID), (mm->bFlags & MODES_ACFLAGS_AOG));
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if (location_result == -2) {
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// Global CPR failed because an airborne position produced implausible results.
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// This is bad data. Discard both odd and even messages and wait for a fresh pair.
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// Also disable aircraft-relative positions until we have a new good position (but don't discard the
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// recorded position itself)
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Modes.stats_current.cpr_global_bad++;
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mm->bFlags &= ~(MODES_ACFLAGS_LATLON_VALID | MODES_ACFLAGS_LLODD_VALID | MODES_ACFLAGS_LLEVEN_VALID);
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a->bFlags &= ~(MODES_ACFLAGS_LATLON_REL_OK | MODES_ACFLAGS_LLODD_VALID | MODES_ACFLAGS_LLEVEN_VALID);
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return;
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} else if (location_result == -1) {
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// No local reference for surface position available, or the two messages crossed a zone.
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// Nonfatal, try again later.
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Modes.stats_current.cpr_global_skipped++;
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} else {
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Modes.stats_current.cpr_global_ok++;
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}
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}
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// Otherwise try relative CPR.
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if (location_result == -1) {
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location_result = doLocalCPR(a, (mm->bFlags & MODES_ACFLAGS_LLODD_VALID), (mm->bFlags & MODES_ACFLAGS_AOG), now);
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if (location_result == -1) {
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Modes.stats_current.cpr_local_skipped++;
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} else {
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Modes.stats_current.cpr_local_ok++;
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mm->bFlags |= MODES_ACFLAGS_REL_CPR_USED;
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}
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}
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if (location_result == 0) {
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// If we sucessfully decoded, back copy the results to mm so that we can print them in list output
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mm->bFlags |= MODES_ACFLAGS_LATLON_VALID;
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mm->fLat = a->lat;
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mm->fLon = a->lon;
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// Update aircraft state
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a->bFlags |= (MODES_ACFLAGS_LATLON_VALID | MODES_ACFLAGS_LATLON_REL_OK);
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a->seenLatLon = a->seen;
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a->timestampLatLon = a->timestamp;
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}
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}
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//
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//=========================================================================
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//
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// Receive new messages and update tracked aircraft state
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//
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struct aircraft *trackUpdateFromMessage(struct modesMessage *mm)
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{
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struct aircraft *a;
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time_t now = time(NULL);
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// Lookup our aircraft or create a new one
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a = trackFindAircraft(mm->addr);
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if (!a) { // If it's a currently unknown aircraft....
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a = trackCreateAircraft(mm); // ., create a new record for it,
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a->next = Modes.aircrafts; // .. and put it at the head of the list
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Modes.aircrafts = a;
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}
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a->signalLevel[a->messages & 7] = mm->signalLevel;// replace the 8th oldest signal strength
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a->seen = now;
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a->timestamp = mm->timestampMsg;
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a->messages++;
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// If a (new) CALLSIGN has been received, copy it to the aircraft structure
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if (mm->bFlags & MODES_ACFLAGS_CALLSIGN_VALID) {
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memcpy(a->flight, mm->flight, sizeof(a->flight));
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}
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// If a (new) ALTITUDE has been received, copy it to the aircraft structure
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if (mm->bFlags & MODES_ACFLAGS_ALTITUDE_VALID) {
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if ( (a->modeCcount) // if we've a modeCcount already
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&& (a->altitude != mm->altitude ) ) // and Altitude has changed
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// && (a->modeC != mm->modeC + 1) // and Altitude not changed by +100 feet
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// && (a->modeC + 1 != mm->modeC ) ) // and Altitude not changes by -100 feet
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{
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a->modeCcount = 0; //....zero the hit count
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a->modeACflags &= ~MODEAC_MSG_MODEC_HIT;
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}
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a->altitude = mm->altitude;
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a->modeC = (mm->altitude + 49) / 100;
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}
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// If a (new) SQUAWK has been received, copy it to the aircraft structure
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if (mm->bFlags & MODES_ACFLAGS_SQUAWK_VALID) {
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if (a->modeA != mm->modeA) {
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a->modeAcount = 0; // Squawk has changed, so zero the hit count
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a->modeACflags &= ~MODEAC_MSG_MODEA_HIT;
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}
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a->modeA = mm->modeA;
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}
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// If a (new) HEADING has been received, copy it to the aircraft structure
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if (mm->bFlags & MODES_ACFLAGS_HEADING_VALID) {
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a->track = mm->heading;
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}
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// If a (new) SPEED has been received, copy it to the aircraft structure
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if (mm->bFlags & MODES_ACFLAGS_SPEED_VALID) {
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a->speed = mm->velocity;
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}
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// If a (new) Vertical Descent rate has been received, copy it to the aircraft structure
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if (mm->bFlags & MODES_ACFLAGS_VERTRATE_VALID) {
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a->vert_rate = mm->vert_rate;
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}
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// if the Aircraft has landed or taken off since the last message, clear the even/odd CPR flags
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if ((mm->bFlags & MODES_ACFLAGS_AOG_VALID) && ((a->bFlags ^ mm->bFlags) & MODES_ACFLAGS_AOG)) {
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a->bFlags &= ~(MODES_ACFLAGS_LLBOTH_VALID | MODES_ACFLAGS_AOG);
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}
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// If we've got a new cprlat or cprlon
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if (mm->bFlags & MODES_ACFLAGS_LLEITHER_VALID) {
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updatePosition(a, mm, now);
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}
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// Update the aircrafts a->bFlags to reflect the newly received mm->bFlags;
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a->bFlags |= mm->bFlags;
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if (mm->msgtype == 32) {
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int flags = a->modeACflags;
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if ((flags & (MODEAC_MSG_MODEC_HIT | MODEAC_MSG_MODEC_OLD)) == MODEAC_MSG_MODEC_OLD) {
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//
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// This Mode-C doesn't currently hit any known Mode-S, but it used to because MODEAC_MSG_MODEC_OLD is
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// set So the aircraft it used to match has either changed altitude, or gone out of our receiver range
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//
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// We've now received this Mode-A/C again, so it must be a new aircraft. It could be another aircraft
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// at the same Mode-C altitude, or it could be a new airctraft with a new Mods-A squawk.
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//
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// To avoid masking this aircraft from the interactive display, clear the MODEAC_MSG_MODES_OLD flag
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// and set messages to 1;
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//
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a->modeACflags = flags & ~MODEAC_MSG_MODEC_OLD;
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a->messages = 1;
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}
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}
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return (a);
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}
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//
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// Periodic updates of tracking state
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//
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//
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//=========================================================================
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//
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// Periodically search through the list of known Mode-S aircraft and tag them if this
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// Mode A/C matches their known Mode S Squawks or Altitudes(+/- 50feet).
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//
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// A Mode S equipped aircraft may also respond to Mode A and Mode C SSR interrogations.
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// We can't tell if this is a Mode A or C, so scan through the entire aircraft list
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// looking for matches on Mode A (squawk) and Mode C (altitude). Flag in the Mode S
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// records that we have had a potential Mode A or Mode C response from this aircraft.
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//
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// If an aircraft responds to Mode A then it's highly likely to be responding to mode C
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// too, and vice verca. Therefore, once the mode S record is tagged with both a Mode A
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// and a Mode C flag, we can be fairly confident that this Mode A/C frame relates to that
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// Mode S aircraft.
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//
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// Mode C's are more likely to clash than Mode A's; There could be several aircraft
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// cruising at FL370, but it's less likely (though not impossible) that there are two
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// aircraft on the same squawk. Therefore, give precidence to Mode A record matches
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//
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// Note : It's theoretically possible for an aircraft to have the same value for Mode A
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// and Mode C. Therefore we have to check BOTH A AND C for EVERY S.
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//
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static void trackUpdateAircraftModeA(struct aircraft *a)
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{
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struct aircraft *b = Modes.aircrafts;
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while(b) {
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if ((b->modeACflags & MODEAC_MSG_FLAG) == 0) { // skip any fudged ICAO records
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// If both (a) and (b) have valid squawks...
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if ((a->bFlags & b->bFlags) & MODES_ACFLAGS_SQUAWK_VALID) {
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// ...check for Mode-A == Mode-S Squawk matches
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if (a->modeA == b->modeA) { // If a 'real' Mode-S ICAO exists using this Mode-A Squawk
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b->modeAcount = a->messages;
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b->modeACflags |= MODEAC_MSG_MODEA_HIT;
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a->modeACflags |= MODEAC_MSG_MODEA_HIT;
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if ( (b->modeAcount > 0) &&
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( (b->modeCcount > 1)
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|| (a->modeACflags & MODEAC_MSG_MODEA_ONLY)) ) // Allow Mode-A only matches if this Mode-A is invalid Mode-C
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{a->modeACflags |= MODEAC_MSG_MODES_HIT;} // flag this ModeA/C probably belongs to a known Mode S
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}
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}
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// If both (a) and (b) have valid altitudes...
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if ((a->bFlags & b->bFlags) & MODES_ACFLAGS_ALTITUDE_VALID) {
|
|
// ... check for Mode-C == Mode-S Altitude matches
|
|
if ( (a->modeC == b->modeC ) // If a 'real' Mode-S ICAO exists at this Mode-C Altitude
|
|
|| (a->modeC == b->modeC + 1) // or this Mode-C - 100 ft
|
|
|| (a->modeC + 1 == b->modeC ) ) { // or this Mode-C + 100 ft
|
|
b->modeCcount = a->messages;
|
|
b->modeACflags |= MODEAC_MSG_MODEC_HIT;
|
|
a->modeACflags |= MODEAC_MSG_MODEC_HIT;
|
|
if ( (b->modeAcount > 0) &&
|
|
(b->modeCcount > 1) )
|
|
{a->modeACflags |= (MODEAC_MSG_MODES_HIT | MODEAC_MSG_MODEC_OLD);} // flag this ModeA/C probably belongs to a known Mode S
|
|
}
|
|
}
|
|
}
|
|
b = b->next;
|
|
}
|
|
}
|
|
//
|
|
//=========================================================================
|
|
//
|
|
static void trackUpdateAircraftModeS()
|
|
{
|
|
struct aircraft *a = Modes.aircrafts;
|
|
|
|
while(a) {
|
|
int flags = a->modeACflags;
|
|
if (flags & MODEAC_MSG_FLAG) { // find any fudged ICAO records
|
|
|
|
// clear the current A,C and S hit bits ready for this attempt
|
|
a->modeACflags = flags & ~(MODEAC_MSG_MODEA_HIT | MODEAC_MSG_MODEC_HIT | MODEAC_MSG_MODES_HIT);
|
|
|
|
trackUpdateAircraftModeA(a); // and attempt to match them with Mode-S
|
|
}
|
|
a = a->next;
|
|
}
|
|
}
|
|
|
|
//
|
|
//=========================================================================
|
|
//
|
|
// If we don't receive new nessages within TRACK_AIRCRAFT_TTL
|
|
// we remove the aircraft from the list.
|
|
//
|
|
static void trackRemoveStaleAircraft(time_t now)
|
|
{
|
|
struct aircraft *a = Modes.aircrafts;
|
|
struct aircraft *prev = NULL;
|
|
|
|
while(a) {
|
|
if ((now - a->seen) > TRACK_AIRCRAFT_TTL ||
|
|
(a->messages == 1 && (now - a->seen) > TRACK_AIRCRAFT_ONEHIT_TTL)) {
|
|
// Remove the element from the linked list, with care
|
|
// if we are removing the first element
|
|
if (!prev) {
|
|
Modes.aircrafts = a->next; free(a); a = Modes.aircrafts;
|
|
} else {
|
|
prev->next = a->next; free(a); a = prev->next;
|
|
}
|
|
} else {
|
|
prev = a; a = a->next;
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
//
|
|
// Entry point for periodic updates
|
|
//
|
|
|
|
void trackPeriodicUpdate()
|
|
{
|
|
static time_t next_update;
|
|
time_t now = time(NULL);
|
|
|
|
// Only do updates once per second
|
|
if (now >= next_update) {
|
|
next_update = now;
|
|
trackRemoveStaleAircraft(now);
|
|
trackUpdateAircraftModeS();
|
|
}
|
|
}
|