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track.c
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// Part of readsb, a Mode-S/ADSB/TIS message decoder.
//
// track.c: aircraft state tracking
//
// Copyright (c) 2019 Michael Wolf <[email protected]>
//
// This code is based on a detached fork of dump1090-fa.
//
// Copyright (c) 2014-2016 Oliver Jowett <[email protected]>
//
// This file 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 of the License, or
// any later version.
//
// This file 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 this program. If not, see <http://www.gnu.org/licenses/>.
//
// This file incorporates work covered by the following copyright and
// license:
//
// Copyright (C) 2012 by Salvatore Sanfilippo <[email protected]>
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "readsb.h"
#include <inttypes.h>
/* #define DEBUG_CPR_CHECKS */
uint32_t modeAC_count[4096];
uint32_t modeAC_lastcount[4096];
uint32_t modeAC_match[4096];
uint32_t modeAC_age[4096];
//
// Return a new aircraft structure for the linked list of tracked
// aircraft
//
static struct aircraft *trackCreateAircraft(struct modesMessage *mm) {
static struct aircraft zeroAircraft;
struct aircraft *a = (struct aircraft *) malloc(sizeof (*a));
int i;
// Default everything to zero/NULL
*a = zeroAircraft;
// Now initialise things that should not be 0/NULL to their defaults
a->addr = mm->addr;
a->addrtype = mm->addrtype;
for (i = 0; i < 8; ++i)
a->signalLevel[i] = 1e-5;
a->signalNext = 0;
// defaults until we see a message otherwise
a->adsb_version = -1;
a->adsb_hrd = HEADING_MAGNETIC;
a->adsb_tah = HEADING_GROUND_TRACK;
// prime FATSV defaults we only emit on change
// start off with the "last emitted" ACAS RA being blank (just the BDS 3,0
// or ES type code)
a->fatsv_emitted_bds_30[0] = 0x30;
a->fatsv_emitted_es_acas_ra[0] = 0xE2;
a->fatsv_emitted_adsb_version = -1;
a->fatsv_emitted_addrtype = ADDR_UNKNOWN;
// don't immediately emit, let some data build up
a->fatsv_last_emitted = a->fatsv_last_force_emit = messageNow();
// Copy the first message so we can emit it later when a second message arrives.
a->first_message = *mm;
// initialize data validity ages
#define F(f,s,e) do { a->f##_valid.stale_interval = (s) * 1000; a->f##_valid.expire_interval = (e) * 1000; } while (0)
F(callsign, 60, 70); // ADS-B or Comm-B
F(altitude_baro, 15, 70); // ADS-B or Mode S
F(altitude_geom, 60, 70); // ADS-B only
F(geom_delta, 60, 70); // ADS-B only
F(gs, 60, 70); // ADS-B or Comm-B
F(ias, 60, 70); // ADS-B (rare) or Comm-B
F(tas, 60, 70); // ADS-B (rare) or Comm-B
F(mach, 60, 70); // Comm-B only
F(track, 60, 70); // ADS-B or Comm-B
F(track_rate, 60, 70); // Comm-B only
F(roll, 60, 70); // Comm-B only
F(mag_heading, 60, 70); // ADS-B (rare) or Comm-B
F(true_heading, 60, 70); // ADS-B only (rare)
F(baro_rate, 60, 70); // ADS-B or Comm-B
F(geom_rate, 60, 70); // ADS-B or Comm-B
F(squawk, 15, 70); // ADS-B or Mode S
F(airground, 15, 70); // ADS-B or Mode S
F(nav_qnh, 60, 70); // Comm-B only
F(nav_altitude_mcp, 60, 70); // ADS-B or Comm-B
F(nav_altitude_fms, 60, 70); // ADS-B or Comm-B
F(nav_altitude_src, 60, 70); // ADS-B or Comm-B
F(nav_heading, 60, 70); // ADS-B or Comm-B
F(nav_modes, 60, 70); // ADS-B or Comm-B
F(cpr_odd, 60, 70); // ADS-B only
F(cpr_even, 60, 70); // ADS-B only
F(position, 60, 70); // ADS-B only
F(nic_a, 60, 70); // ADS-B only
F(nic_c, 60, 70); // ADS-B only
F(nic_baro, 60, 70); // ADS-B only
F(nac_p, 60, 70); // ADS-B only
F(nac_v, 60, 70); // ADS-B only
F(sil, 60, 70); // ADS-B only
F(gva, 60, 70); // ADS-B only
F(sda, 60, 70); // ADS-B only
#undef F
Modes.stats_current.unique_aircraft++;
return (a);
}
//
//=========================================================================
//
// Return the aircraft with the specified address, or NULL if no aircraft
// exists with this address.
//
static struct aircraft *trackFindAircraft(uint32_t addr) {
struct aircraft *a = Modes.aircrafts[addr % AIRCRAFTS_BUCKETS];
while (a) {
if (a->addr == addr) return (a);
a = a->next;
}
return (NULL);
}
// Should we accept some new data from the given source?
// If so, update the validity and return 1
static int accept_data(data_validity *d, datasource_t source) {
if (messageNow() < d->updated)
return 0;
if (source < d->source && messageNow() < d->stale)
return 0;
d->source = source;
d->updated = messageNow();
d->stale = messageNow() + (d->stale_interval ? d->stale_interval : 60000);
d->expires = messageNow() + (d->expire_interval ? d->expire_interval : 70000);
return 1;
}
// Given two datasources, produce a third datasource for data combined from them.
static void combine_validity(data_validity *to, const data_validity *from1, const data_validity *from2) {
if (from1->source == SOURCE_INVALID) {
*to = *from2;
return;
}
if (from2->source == SOURCE_INVALID) {
*to = *from1;
return;
}
to->source = (from1->source < from2->source) ? from1->source : from2->source; // the worse of the two input sources
to->updated = (from1->updated > from2->updated) ? from1->updated : from2->updated; // the *later* of the two update times
to->stale = (from1->stale < from2->stale) ? from1->stale : from2->stale; // the earlier of the two stale times
to->expires = (from1->expires < from2->expires) ? from1->expires : from2->expires; // the earlier of the two expiry times
}
static int compare_validity(const data_validity *lhs, const data_validity *rhs) {
if (messageNow() < lhs->stale && lhs->source > rhs->source)
return 1;
else if (messageNow() < rhs->stale && lhs->source < rhs->source)
return -1;
else if (lhs->updated > rhs->updated)
return 1;
else if (lhs->updated < rhs->updated)
return -1;
else
return 0;
}
//
// CPR position updating
//
// Distance between points on a spherical earth.
// This has up to 0.5% error because the earth isn't actually spherical
// (but we don't use it in situations where that matters)
static double greatcircle(double lat0, double lon0, double lat1, double lon1) {
double dlat, dlon;
lat0 = lat0 * M_PI / 180.0;
lon0 = lon0 * M_PI / 180.0;
lat1 = lat1 * M_PI / 180.0;
lon1 = lon1 * M_PI / 180.0;
dlat = fabs(lat1 - lat0);
dlon = fabs(lon1 - lon0);
// use haversine for small distances for better numerical stability
if (dlat < 0.001 && dlon < 0.001) {
double a = sin(dlat / 2) * sin(dlat / 2) + cos(lat0) * cos(lat1) * sin(dlon / 2) * sin(dlon / 2);
return 6371e3 * 2 * atan2(sqrt(a), sqrt(1.0 - a));
}
// spherical law of cosines
return 6371e3 * acos(sin(lat0) * sin(lat1) + cos(lat0) * cos(lat1) * cos(dlon));
}
static void update_range_histogram(double lat, double lon) {
double range = 0;
int valid_latlon = Modes.bUserFlags & MODES_USER_LATLON_VALID;
if (!valid_latlon)
return;
range = greatcircle(Modes.fUserLat, Modes.fUserLon, lat, lon);
if ((range <= Modes.maxRange || Modes.maxRange == 0) && range > Modes.stats_current.longest_distance) {
Modes.stats_current.longest_distance = range;
}
if (Modes.stats_range_histo) {
int bucket = round(range / Modes.maxRange * RANGE_BUCKET_COUNT);
if (bucket < 0)
bucket = 0;
else if (bucket >= RANGE_BUCKET_COUNT)
bucket = RANGE_BUCKET_COUNT - 1;
++Modes.stats_current.range_histogram[bucket];
}
}
// return true if it's OK for the aircraft to have travelled from its last known position
// to a new position at (lat,lon,surface) at a time of now.
static int speed_check(struct aircraft *a, double lat, double lon, int surface) {
uint64_t elapsed;
double distance;
double range;
int speed;
int inrange;
if (!trackDataValid(&a->position_valid))
return 1; // no reference, assume OK
elapsed = trackDataAge(&a->position_valid);
if (trackDataValid(&a->gs_valid)) {
// use the larger of the current and earlier speed
speed = (a->gs_last_pos > a->gs) ? a->gs_last_pos : a->gs;
// add 2 knots for every second we haven't known the speed
speed = speed + (2*trackDataAge(&a->gs_valid)/1000.0);
} else if (trackDataValid(&a->tas_valid)) {
speed = a->tas * 4 / 3;
} else if (trackDataValid(&a->ias_valid)) {
speed = a->ias * 2;
} else {
speed = surface ? 100 : 700; // guess
}
// Work out a reasonable speed to use:
// current speed + 1/3
// surface speed min 20kt, max 150kt
// airborne speed min 200kt, no max
speed = speed * 4 / 3;
if (surface) {
if (speed < 20)
speed = 20;
if (speed > 150)
speed = 150;
} else {
if (speed < 200)
speed = 200;
}
// 100m (surface) or 500m (airborne) base distance to allow for minor errors,
// plus distance covered at the given speed for the elapsed time + 1 second.
range = (surface ? 0.1e3 : 0.5e3) + ((elapsed + 1000.0) / 1000.0) * (speed * 1852.0 / 3600.0);
// find actual distance
distance = greatcircle(a->lat, a->lon, lat, lon);
inrange = (distance <= range);
#ifdef DEBUG_CPR_CHECKS
if (!inrange) {
fprintf(stderr, "Speed check failed: %06x: %.3f,%.3f -> %.3f,%.3f in %.1f seconds, max speed %d kt, range %.1fkm, actual %.1fkm\n",
a->addr, a->lat, a->lon, lat, lon, elapsed / 1000.0, speed, range / 1000.0, distance / 1000.0);
}
#endif
return inrange;
}
static int doGlobalCPR(struct aircraft *a, struct modesMessage *mm, double *lat, double *lon, unsigned *nic, unsigned *rc) {
int result;
int fflag = mm->cpr_odd;
int surface = (mm->cpr_type == CPR_SURFACE);
// derive NIC, Rc from the worse of the two position
// smaller NIC is worse; larger Rc is worse
*nic = (a->cpr_even_nic < a->cpr_odd_nic ? a->cpr_even_nic : a->cpr_odd_nic);
*rc = (a->cpr_even_rc > a->cpr_odd_rc ? a->cpr_even_rc : a->cpr_odd_rc);
if (surface) {
// surface global CPR
// find reference location
double reflat, reflon;
if (a->pos_set) { // Ok to try aircraft relative first
reflat = a->lat;
reflon = a->lon;
} else if (Modes.bUserFlags & MODES_USER_LATLON_VALID) {
reflat = Modes.fUserLat;
reflon = Modes.fUserLon;
} else {
// No local reference, give up
return (-1);
}
result = decodeCPRsurface(reflat, reflon,
a->cpr_even_lat, a->cpr_even_lon,
a->cpr_odd_lat, a->cpr_odd_lon,
fflag,
lat, lon);
} else {
// airborne global CPR
result = decodeCPRairborne(a->cpr_even_lat, a->cpr_even_lon,
a->cpr_odd_lat, a->cpr_odd_lon,
fflag,
lat, lon);
}
if (result < 0) {
#ifdef DEBUG_CPR_CHECKS
fprintf(stderr, "CPR: decode failure for %06X (%d).\n", a->addr, result);
fprintf(stderr, " even: %d %d odd: %d %d fflag: %s\n",
a->cpr_even_lat, a->cpr_even_lon,
a->cpr_odd_lat, a->cpr_odd_lon,
fflag ? "odd" : "even");
#endif
return result;
}
// check max range
if (Modes.maxRange > 0 && (Modes.bUserFlags & MODES_USER_LATLON_VALID)) {
double range = greatcircle(Modes.fUserLat, Modes.fUserLon, *lat, *lon);
if (range > Modes.maxRange) {
#ifdef DEBUG_CPR_CHECKS
fprintf(stderr, "Global range check failed: %06x: %.3f,%.3f, max range %.1fkm, actual %.1fkm\n",
a->addr, *lat, *lon, Modes.maxRange / 1000.0, range / 1000.0);
#endif
Modes.stats_current.cpr_global_range_checks++;
return (-2); // we consider an out-of-range value to be bad data
}
}
// for mlat results, skip the speed check
if (mm->source == SOURCE_MLAT)
return result;
// check speed limit
if (trackDataValid(&a->position_valid) && mm->source <= a->position_valid.source && !speed_check(a, *lat, *lon, surface)) {
Modes.stats_current.cpr_global_speed_checks++;
return -2;
}
return result;
}
static int doLocalCPR(struct aircraft *a, struct modesMessage *mm, double *lat, double *lon, unsigned *nic, unsigned *rc) {
// relative CPR
// find reference location
double reflat, reflon;
double range_limit = 0;
int result;
int fflag = mm->cpr_odd;
int surface = (mm->cpr_type == CPR_SURFACE);
int relative_to = 0; // aircraft(1) or receiver(2) relative
if (fflag) {
*nic = a->cpr_odd_nic;
*rc = a->cpr_odd_rc;
} else {
*nic = a->cpr_even_nic;
*rc = a->cpr_even_rc;
}
if (messageNow() - a->position_valid.updated < (10*60*1000)) {
reflat = a->lat;
reflon = a->lon;
if (a->pos_nic < *nic)
*nic = a->pos_nic;
if (a->pos_rc < *rc)
*rc = a->pos_rc;
range_limit = 1852*100; // 100NM
// 100 NM in the 10 minutes of position validity means 600 knots which
// is fast but happens even for commercial airliners.
// It's not a problem if this limitation fails every now and then.
// A wrong relative position decode would require the aircraft to
// travel 360-100=260 NM in the 10 minutes of position validity.
// This is impossible for planes slower than 1560 knots/Mach 2.3 over the ground.
// Thus this range limit combined with the 10 minutes of position
// validity should not provide bad positions (1 cell away).
relative_to = 1;
} else if (!surface && (Modes.bUserFlags & MODES_USER_LATLON_VALID)) {
reflat = Modes.fUserLat;
reflon = Modes.fUserLon;
// The cell size is at least 360NM, giving a nominal
// max range of 180NM (half a cell).
//
// If the receiver range is more than half a cell
// then we must limit this range further to avoid
// ambiguity. (e.g. if we receive a position report
// at 200NM distance, this may resolve to a position
// at (200-360) = 160NM in the wrong direction)
if (Modes.maxRange == 0) {
return (-1); // Can't do receiver-centered checks at all
} else if (Modes.maxRange <= 1852 * 180) {
range_limit = Modes.maxRange;
} else if (Modes.maxRange < 1852 * 360) {
range_limit = (1852 * 360) - Modes.maxRange;
} else {
return (-1); // Can't do receiver-centered checks at all
}
relative_to = 2;
} else {
// No local reference, give up
return (-1);
}
result = decodeCPRrelative(reflat, reflon,
mm->cpr_lat,
mm->cpr_lon,
fflag, surface,
lat, lon);
if (result < 0) {
return result;
}
// check range limit
if (range_limit > 0) {
double range = greatcircle(reflat, reflon, *lat, *lon);
if (range > range_limit) {
Modes.stats_current.cpr_local_range_checks++;
return (-1);
}
}
// check speed limit
if (trackDataValid(&a->position_valid) && mm->source <= a->position_valid.source && !speed_check(a, *lat, *lon, surface)) {
#ifdef DEBUG_CPR_CHECKS
fprintf(stderr, "Speed check for %06X with local decoding failed\n", a->addr);
#endif
Modes.stats_current.cpr_local_speed_checks++;
return -1;
}
return relative_to;
}
static uint64_t time_between(uint64_t t1, uint64_t t2) {
if (t1 >= t2)
return t1 - t2;
else
return t2 - t1;
}
static void updatePosition(struct aircraft *a, struct modesMessage *mm) {
int location_result = -1;
uint64_t max_elapsed;
double new_lat = 0, new_lon = 0;
unsigned new_nic = 0;
unsigned new_rc = 0;
int surface;
surface = (mm->cpr_type == CPR_SURFACE);
if (surface) {
++Modes.stats_current.cpr_surface;
// Surface: 25 seconds if >25kt or speed unknown, 50 seconds otherwise
if (mm->gs_valid && mm->gs.selected <= 25)
max_elapsed = 50000;
else
max_elapsed = 25000;
} else {
++Modes.stats_current.cpr_airborne;
// Airborne: 10 seconds
max_elapsed = 10000;
}
// If we have enough recent data, try global CPR
if (trackDataValid(&a->cpr_odd_valid) && trackDataValid(&a->cpr_even_valid) &&
a->cpr_odd_valid.source == a->cpr_even_valid.source &&
a->cpr_odd_type == a->cpr_even_type &&
time_between(a->cpr_odd_valid.updated, a->cpr_even_valid.updated) <= max_elapsed) {
location_result = doGlobalCPR(a, mm, &new_lat, &new_lon, &new_nic, &new_rc);
if (location_result == -2) {
#ifdef DEBUG_CPR_CHECKS
fprintf(stderr, "global CPR failure (invalid) for (%06X).\n", a->addr);
#endif
// Global CPR failed because the position produced implausible results.
// This is bad data.
// At least one of the CPRs is bad, mark them both invalid.
// If we are not confident in the position, invalidate it as well.
Modes.stats_current.cpr_global_bad++;
a->cpr_odd_valid.source = SOURCE_INVALID;
a->cpr_even_valid.source = SOURCE_INVALID;
a->pos_reliable_odd--;
a->pos_reliable_even--;
if (a->pos_reliable_odd <= 0 || a->pos_reliable_even <=0) {
a->position_valid.source = SOURCE_INVALID;
a->pos_reliable_odd = 0;
a->pos_reliable_even = 0;
}
return;
} else if (location_result == -1) {
#ifdef DEBUG_CPR_CHECKS
if (mm->source == SOURCE_MLAT) {
fprintf(stderr, "CPR skipped from MLAT (%06X).\n", a->addr);
}
#endif
// No local reference for surface position available, or the two messages crossed a zone.
// Nonfatal, try again later.
Modes.stats_current.cpr_global_skipped++;
} else {
if (accept_data(&a->position_valid, mm->source)) {
Modes.stats_current.cpr_global_ok++;
if (a->pos_reliable_odd <= 0 || a->pos_reliable_even <=0) {
a->pos_reliable_odd = 1;
a->pos_reliable_even = 1;
} else if (mm->cpr_odd) {
a->pos_reliable_odd = min(a->pos_reliable_odd + 1, Modes.filter_persistence);
} else {
a->pos_reliable_even = min(a->pos_reliable_even + 1, Modes.filter_persistence);
a->pos_set = 1;
}
if (trackDataValid(&a->gs_valid))
a->gs_last_pos = a->gs;
} else {
Modes.stats_current.cpr_global_skipped++;
location_result = -2;
}
}
}
// Otherwise try relative CPR.
if (location_result == -1) {
location_result = doLocalCPR(a, mm, &new_lat, &new_lon, &new_nic, &new_rc);
if (location_result >= 0 && accept_data(&a->position_valid, mm->source)) {
Modes.stats_current.cpr_local_ok++;
mm->cpr_relative = 1;
if (trackDataValid(&a->gs_valid))
a->gs_last_pos = a->gs;
if (location_result == 1) {
Modes.stats_current.cpr_local_aircraft_relative++;
}
if (location_result == 2) {
Modes.stats_current.cpr_local_receiver_relative++;
}
} else {
Modes.stats_current.cpr_local_skipped++;
location_result = -1;
}
}
if (location_result >= 0) {
// If we sucessfully decoded, back copy the results to mm so that we can print them in list output
mm->cpr_decoded = 1;
mm->decoded_lat = new_lat;
mm->decoded_lon = new_lon;
mm->decoded_nic = new_nic;
mm->decoded_rc = new_rc;
// Update aircraft state
a->lat = new_lat;
a->lon = new_lon;
a->pos_nic = new_nic;
a->pos_rc = new_rc;
if (a->pos_reliable_odd >= 2 && a->pos_reliable_even >= 2 && mm->source == SOURCE_ADSB) {
update_range_histogram(new_lat, new_lon);
}
}
}
static unsigned compute_nic(unsigned metype, unsigned version, unsigned nic_a, unsigned nic_b, unsigned nic_c) {
switch (metype) {
case 5: // surface
case 9: // airborne
case 20: // airborne, GNSS altitude
return 11;
case 6: // surface
case 10: // airborne
case 21: // airborne, GNSS altitude
return 10;
case 7: // surface
if (version == 2) {
if (nic_a && !nic_c) {
return 9;
} else {
return 8;
}
} else if (version == 1) {
if (nic_a) {
return 9;
} else {
return 8;
}
} else {
return 8;
}
case 8: // surface
if (version == 2) {
if (nic_a && nic_c) {
return 7;
} else if (nic_a && !nic_c) {
return 6;
} else if (!nic_a && nic_c) {
return 6;
} else {
return 0;
}
} else {
return 0;
}
case 11: // airborne
if (version == 2) {
if (nic_a && nic_b) {
return 9;
} else {
return 8;
}
} else if (version == 1) {
if (nic_a) {
return 9;
} else {
return 8;
}
} else {
return 8;
}
case 12: // airborne
return 7;
case 13: // airborne
return 6;
case 14: // airborne
return 5;
case 15: // airborne
return 4;
case 16: // airborne
if (nic_a && nic_b) {
return 3;
} else {
return 2;
}
case 17: // airborne
return 1;
default:
return 0;
}
}
static unsigned compute_rc(unsigned metype, unsigned version, unsigned nic_a, unsigned nic_b, unsigned nic_c) {
switch (metype) {
case 5: // surface
case 9: // airborne
case 20: // airborne, GNSS altitude
return 8; // 7.5m
case 6: // surface
case 10: // airborne
case 21: // airborne, GNSS altitude
return 25;
case 7: // surface
if (version == 2) {
if (nic_a && !nic_c) {
return 75;
} else {
return 186; // 185.2m, 0.1NM
}
} else if (version == 1) {
if (nic_a) {
return 75;
} else {
return 186; // 185.2m, 0.1NM
}
} else {
return 186; // 185.2m, 0.1NM
}
case 8: // surface
if (version == 2) {
if (nic_a && nic_c) {
return 371; // 370.4m, 0.2NM
} else if (nic_a && !nic_c) {
return 556; // 555.6m, 0.3NM
} else if (!nic_a && nic_c) {
return 926; // 926m, 0.5NM
} else {
return RC_UNKNOWN;
}
} else {
return RC_UNKNOWN;
}
case 11: // airborne
if (version == 2) {
if (nic_a && nic_b) {
return 75;
} else {
return 186; // 370.4m, 0.2NM
}
} else if (version == 1) {
if (nic_a) {
return 75;
} else {
return 186; // 370.4m, 0.2NM
}
} else {
return 186; // 370.4m, 0.2NM
}
case 12: // airborne
return 371; // 370.4m, 0.2NM
case 13: // airborne
if (version == 2) {
if (!nic_a && nic_b) {
return 556; // 555.6m, 0.3NM
} else if (!nic_a && !nic_b) {
return 926; // 926m, 0.5NM
} else if (nic_a && nic_b) {
return 1112; // 1111.2m, 0.6NM
} else {
return RC_UNKNOWN; // bad combination, assume worst Rc
}
} else if (version == 1) {
if (nic_a) {
return 1112; // 1111.2m, 0.6NM
} else {
return 926; // 926m, 0.5NM
}
} else {
return 926; // 926m, 0.5NM
}
case 14: // airborne
return 1852; // 1.0NM
case 15: // airborne
return 3704; // 2NM
case 16: // airborne
if (version == 2) {
if (nic_a && nic_b) {
return 7408; // 4NM
} else {
return 14816; // 8NM
}
} else if (version == 1) {
if (nic_a) {
return 7408; // 4NM
} else {
return 14816; // 8NM
}
} else {
return 18520; // 10NM
}
case 17: // airborne
return 37040; // 20NM
default:
return RC_UNKNOWN;
}
}
static void compute_nic_rc_from_message(struct modesMessage *mm, struct aircraft *a, unsigned *nic, unsigned *rc) {
int nic_a = (trackDataValid(&a->nic_a_valid) && a->nic_a);
int nic_b = (mm->accuracy.nic_b_valid && mm->accuracy.nic_b);
int nic_c = (trackDataValid(&a->nic_c_valid) && a->nic_c);
*nic = compute_nic(mm->metype, a->adsb_version, nic_a, nic_b, nic_c);
*rc = compute_rc(mm->metype, a->adsb_version, nic_a, nic_b, nic_c);
}
static int altitude_to_feet(int raw, altitude_unit_t unit) {
switch (unit) {
case UNIT_METERS:
return raw / 0.3048;
case UNIT_FEET:
return raw;
default:
return 0;
}
}
//
//=========================================================================
//
// Receive new messages and update tracked aircraft state
//
struct aircraft *trackUpdateFromMessage(struct modesMessage *mm) {
struct aircraft *a;
unsigned int cpr_new = 0;
if (mm->msgtype == 32) {
// Mode A/C, just count it (we ignore SPI)
modeAC_count[modeAToIndex(mm->squawk)]++;
return NULL;
}
if (mm->addr == 0) {
// junk address, don't track it
return NULL;
}
_messageNow = mm->sysTimestampMsg;
// Lookup our aircraft or create a new one
a = trackFindAircraft(mm->addr);
if (!a) { // If it's a currently unknown aircraft....
a = trackCreateAircraft(mm); // ., create a new record for it,
a->next = Modes.aircrafts[mm->addr % AIRCRAFTS_BUCKETS]; // .. and put it at the head of the list
Modes.aircrafts[mm->addr % AIRCRAFTS_BUCKETS] = a;
}
if (mm->signalLevel > 0) {
a->signalLevel[a->signalNext] = mm->signalLevel;
a->signalNext = (a->signalNext + 1) & 7;
}
a->seen = messageNow();
a->messages++;
// update addrtype, we only ever go towards "more direct" types
if (mm->addrtype < a->addrtype)
a->addrtype = mm->addrtype;
// if we saw some direct ADS-B for the first time, assume version 0
if (mm->source == SOURCE_ADSB && a->adsb_version < 0)
a->adsb_version = 0;
// category shouldn't change over time, don't bother with metadata
if (mm->category_valid) {
a->category = mm->category;
}
// operational status message
// done early to update version / HRD / TAH
if (mm->opstatus.valid) {
a->adsb_version = mm->opstatus.version;
if (mm->opstatus.hrd != HEADING_INVALID) {
a->adsb_hrd = mm->opstatus.hrd;
}
if (mm->opstatus.tah != HEADING_INVALID) {
a->adsb_tah = mm->opstatus.tah;
}
}
if (mm->altitude_baro_valid) {
int alt = altitude_to_feet(mm->altitude_baro, mm->altitude_baro_unit);
if (a->modeC_hit) {
int new_modeC = (a->altitude_baro + 49) / 100;
int old_modeC = (alt + 49) / 100;
if (new_modeC != old_modeC) {
a->modeC_hit = 0;
}
}
int delta = alt - a->altitude_baro;
int fpm = 0;
int max_fpm = 12500;
int min_fpm = -12500;
if (abs(delta) >= 300) {
fpm = delta*60*10/(abs((int)trackDataAge(&a->altitude_baro_valid)/100)+10);
if (trackDataValid(&a->geom_rate_valid) && trackDataAge(&a->geom_rate_valid) < trackDataAge(&a->baro_rate_valid)) {
min_fpm = a->geom_rate - 1500 - min(11000, ((int)trackDataAge(&a->geom_rate_valid)/2));
max_fpm = a->geom_rate + 1500 + min(11000, ((int)trackDataAge(&a->geom_rate_valid)/2));
} else if (trackDataValid(&a->baro_rate_valid)) {
min_fpm = a->baro_rate - 1500 - min(11000, ((int)trackDataAge(&a->baro_rate_valid)/2));
max_fpm = a->baro_rate + 1500 + min(11000, ((int)trackDataAge(&a->baro_rate_valid)/2));
}
if (trackDataValid(&a->altitude_baro_valid) && trackDataAge(&a->altitude_baro_valid) < 30000) {
a->altitude_baro_reliable = min(
ALTITUDE_BARO_RELIABLE_MAX - (ALTITUDE_BARO_RELIABLE_MAX*trackDataAge(&a->altitude_baro_valid)/30000),
a->altitude_baro_reliable);
} else {
a->altitude_baro_reliable = 0;
}
}
int good_crc = (mm->crc == 0 && mm->source != SOURCE_MLAT) ? (ALTITUDE_BARO_RELIABLE_MAX/2 - 1) : 0;
if (a->altitude_baro_reliable <= 0 || abs(delta) < 300
|| (fpm < max_fpm && fpm > min_fpm)
|| (good_crc && a->altitude_baro_reliable <= (ALTITUDE_BARO_RELIABLE_MAX/2 + 2))
) {
if (accept_data(&a->altitude_baro_valid, mm->source)) {
a->altitude_baro_reliable = min(ALTITUDE_BARO_RELIABLE_MAX , a->altitude_baro_reliable + (good_crc+1));
/*if (abs(delta) > 2000 && delta != alt) {
fprintf(stderr, "Alt change B: %06x: %d %d -> %d, min %.1f kfpm, max %.1f kfpm, actual %.1f kfpm\n",
a->addr, a->altitude_baro_reliable, a->altitude_baro, alt, min_fpm/1000.0, max_fpm/1000.0, fpm/1000.0);
}*/
a->altitude_baro = alt;
}
} else {
a->altitude_baro_reliable = a->altitude_baro_reliable - (good_crc+1);
//fprintf(stderr, "Alt check F: %06x: %d %d -> %d, min %.1f kfpm, max %.1f kfpm, actual %.1f kfpm\n",
// a->addr, a->altitude_baro_reliable, a->altitude_baro, alt, min_fpm/1000.0, max_fpm/1000.0, fpm/1000.0);
if (a->altitude_baro_reliable <= 0) {
//fprintf(stderr, "Altitude INVALIDATED: %06x\n", a->addr);
a->altitude_baro_reliable = 0;
a->altitude_baro_valid.source = SOURCE_INVALID;
}
}
}
if (mm->squawk_valid && accept_data(&a->squawk_valid, mm->source)) {
if (mm->squawk != a->squawk) {
a->modeA_hit = 0;
}
a->squawk = mm->squawk;
#if 0 // Disabled for now as it obscures the origin of the data
// Handle 7x00 without a corresponding emergency status
if (!mm->emergency_valid) {
emergency_t squawk_emergency;
switch (mm->squawk) {
case 0x7500:
squawk_emergency = EMERGENCY_UNLAWFUL;
break;
case 0x7600:
squawk_emergency = EMERGENCY_NORDO;