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traffic.go
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traffic.go
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/*
Copyright (c) 2015-2016 Christopher Young
Distributable under the terms of The "BSD New" License
that can be found in the LICENSE file, herein included
as part of this header.
traffic.go: Target management, UAT downlink message processing, 1090ES source input, GDL90 traffic reports.
*/
package main
import (
"bufio"
"encoding/hex"
"encoding/json"
"fmt"
"log"
"math"
"net"
"strconv"
"strings"
"sync"
"time"
"github.com/b3nn0/stratux/common"
)
//-0b2b48fe3aef1f88621a0856110a31c01105c4e6c4e6c40a9a820300000000000000;rs=7;
/*
HDR:
MDB Type: 1
Address: 2B48FE (TIS-B track file address)
SV:
NIC: 6
Latitude: +41.4380
Longitude: -84.1056
Altitude: 2300 ft (barometric)
N/S velocity: -65 kt
E/W velocity: -98 kt
Track: 236
Speed: 117 kt
Vertical rate: 0 ft/min (from barometric altitude)
UTC coupling: no
TIS-B site ID: 1
MS:
Emitter category: No information
Callsign: unavailable
Emergency status: No emergency
UAT version: 2
SIL: 2
Transmit MSO: 38
NACp: 8
NACv: 1
NICbaro: 0
Capabilities:
Active modes:
Target track type: true heading
AUXSV:
Sec. altitude: unavailable
*/
const (
TRAFFIC_SOURCE_1090ES = 1
TRAFFIC_SOURCE_UAT = 2
TRAFFIC_SOURCE_OGN = 4
TRAFFIC_SOURCE_AIS = 8
TARGET_TYPE_MODE_S = 0
TARGET_TYPE_ADSB = 1
TARGET_TYPE_ADSR = 2
// Assign next type to UAT messages with address qualifier == 2
// (code corresponds to any UAT GBT targets with Mode S addresses.
// These will be displayed with the airplane icon on the traffic UI page.
// If we see a proper emitter category and NIC > 7, they'll be reassigned to TYPE_ADSR.
TARGET_TYPE_TISB_S = 3
TARGET_TYPE_TISB = 4
TARGET_TYPE_AIS = 5
)
type TrafficInfo struct {
Icao_addr uint32
Reg string // Registration. Calculated from Icao_addr for civil aircraft of US registry.
Tail string // Callsign. Transmitted by aircraft.
Emitter_category uint8 // Formatted using GDL90 standard, e.g. in a Mode ES report, A7 becomes 0x07, B0 becomes 0x08, etc.
SurfaceVehicleType uint16 // Type of service vehicle (when Emitter_category==18) 0..255 is reserved for AIS vessels
OnGround bool // Air-ground status. On-ground is "true".
Addr_type uint8 // UAT address qualifier. Used by GDL90 format, so translations for ES TIS-B/ADS-R are needed.
TargetType uint8 // types decribed in const above
SignalLevel float64 // Signal level, dB RSSI.
SignalLevelHist []float64 // last 8 values. For 1090ES we store the last 8 values here. SignalLevel will then become the minimum of these to get more stable data with antenna diversity
Squawk int // Squawk code
Position_valid bool //TODO: set when position report received. Unset after n seconds?
Lat float32 // decimal common.Degrees, north positive
Lng float32 // decimal common.Degrees, east positive
Alt int32 // Pressure altitude, feet
GnssDiffFromBaroAlt int32 // GNSS altitude above WGS84 datum. Reported in TC 20-22 messages
AltIsGNSS bool // Pressure alt = 0; GNSS alt = 1
NIC int // Navigation Integrity Category.
NACp int // Navigation Accuracy Category for Position.
Track float32 // common.Degrees true
TurnRate float32 // Turn rate in deg/sec (negative = turning left, positive = right)
Speed uint16 // knots
Speed_valid bool // set when speed report received.
Vvel int16 // feet per minute
Timestamp time.Time // timestamp of traffic message, UTC
PriorityStatus uint8 // Emergency or priority code as defined in GDL90 spec, DO-260B (Type 28 msg) and DO-282B
// Parameters starting at 'Age' are calculated from last message receipt on each call of sendTrafficUpdates().
// Mode S transmits position and track in separate messages, and altitude can also be
// received from interrogations.
Age float64 // Age of last valid position fix or last Mode-S transmission, seconds ago.
AgeLastAlt float64 // Age of last altitude message, seconds ago.
Last_seen time.Time // Time of last position update (stratuxClock) or Mode-S transmission. Used for timing out expired data.
Last_alt time.Time // Time of last altitude update (stratuxClock).
Last_GnssDiff time.Time // Time of last GnssDiffFromBaroAlt update (stratuxClock).
Last_GnssDiffAlt int32 // Altitude at last GnssDiffFromBaroAlt update.
Last_speed time.Time // Time of last velocity and track update (stratuxClock).
Last_source uint8 // Last frequency on which this target was received.
ExtrapolatedPosition bool //TODO: True if Stratux is "coasting" the target from last known position.
Last_extrapolation time.Time
AgeExtrapolation float64
Lat_fix float32 // Last real, non-extrapolated latitude
Lng_fix float32 // Last real, non-extrapolated longitude
Alt_fix int32 // Last real, non-extrapolated altitude
BearingDist_valid bool // set when bearing and distance information is valid
Bearing float64 // Bearing in common.Degrees true to traffic from ownship, if it can be calculated. Units: common.Degrees.
Distance float64 // Distance to traffic from ownship, if it can be calculated. Units: meters.
DistanceEstimated float64 // Estimated distance of the target if real distance can't be calculated, Estimated from signal strength with exponential smoothing.
DistanceEstimatedLastTs time.Time // Used to compute moving average
ReceivedMsgs uint64 // Number of messages received by this aircraft
IsStratux bool // Target is equipped with a Stratux that transmits via OGN tracker
//FIXME: Rename variables for consistency, especially "Last_".
}
type dump1090Data struct {
Icao_addr uint32
DF int // Mode S downlink format.
CA int // Lowest 3 bits of first byte of Mode S message (DF11 and DF17 capability; DF18 control field, zero for all other DF types)
TypeCode int // Mode S type code
SubtypeCode int // Mode S subtype code
SBS_MsgType int // type of SBS message (used in "old" 1090 parsing)
SignalLevel float64 // Decimal RSSI (0-1 nominal) as reported by dump1090-mutability. Convert to dB RSSI before setting in TrafficInfo.
Tail *string
Squawk *int // 12-bit squawk code in octal format
Emitter_category *int
OnGround *bool
Lat *float32
Lng *float32
Position_valid bool
NACp *int
Alt *int
AltIsGNSS bool //
GnssDiffFromBaroAlt *int16 // GNSS height above baro altitude in feet; valid range is -3125 to 3125. +/- 3138 indicates larger difference.
Vvel *int16
Speed_valid bool
Speed *uint16
Track *uint16
Timestamp time.Time // time traffic last seen, UTC
}
type esmsg struct {
TimeReceived time.Time
Data string
}
var traffic map[uint32]TrafficInfo
var trafficMutex *sync.Mutex
var seenTraffic map[uint32]bool // Historical list of all ICAO addresses seen.
var OwnshipTrafficInfo TrafficInfo
func convertFeetToMeters(feet float32) float32 {
return feet * 0.3048
}
func convertMetersToFeet(meters float32) float32 {
return meters / 0.3048
}
func cleanupOldEntries() {
for key, ti := range traffic {
if ti.Last_source != TRAFFIC_SOURCE_AIS && stratuxClock.Since(ti.Last_seen).Seconds() > 60 { // keep it in the database for up to 60 seconds, so we don't lose tail number, etc...
delete(traffic, key)
}
if ti.Last_source == TRAFFIC_SOURCE_AIS && stratuxClock.Since(ti.Last_seen).Seconds() > 60*15 { // keep it in the database for up to 15 minutes, so we don't lose tail number, etc...
delete(traffic, key)
}
}
}
func removeTarget(id uint32) {
trafficMutex.Lock()
defer trafficMutex.Unlock()
if val, ok := traffic[id]; ok {
// Make sure the web interface times it out..
val.Age = 60
val.Position_valid = false
registerTrafficUpdate(val)
delete(traffic, id)
}
}
// Checks if the given TrafficInfo is our ownship. As the user can specify multiple ownship
// hex codes, this is able to smartly identify if it really is our ownship.
// If the ti is very close and at same altitude, it is considered to be us
// If it has no position information, we will not take it as ownship, but ignore its data (no mode-s detection for everything that is configured as ownship)
func isOwnshipTrafficInfo(ti TrafficInfo) (isOwnshipInfo bool, shouldIgnore bool) {
// First, check if this is our own OGN tracker
if (globalStatus.GPS_detected_type & 0x0f) == GPS_TYPE_OGNTRACKER {
ognTrackerCodeInt, _ := strconv.ParseUint(globalSettings.OGNAddr, 16, 32)
prevTrackerCodeInt, _ := strconv.ParseUint(globalStatus.OGNPrevRandomAddr, 16, 32)
if uint32(ognTrackerCodeInt) == ti.Icao_addr || uint32(prevTrackerCodeInt) == ti.Icao_addr {
isOwnshipInfo = !isGPSValid() // only use OGN tracker as ownship position if we are not equipped with a GPS..
shouldIgnore = true
return
}
}
codes := strings.Split(globalSettings.OwnshipModeS, ",")
shouldIgnore = false
for _, ownCode := range codes {
ownCodeInt, _ := strconv.ParseInt(strings.Trim(ownCode, " "), 16, 32)
if uint32(ownCodeInt) == ti.Icao_addr {
if !ti.Position_valid {
// Can't verify the ownship, ignore it for bearingless display
shouldIgnore = true
continue
}
// User might have specified the address of another airplane that he regularly flys.
// If this airplane is currently in the air and we receive it, it gets priority over our ownship information.
// This is a sanity check to filter out such cases - only accept the ownship data if
// it somewhat matches our real data
// because of second-resolution in flarm we assume worst case of +1 second
timeDiff := math.Abs(ti.Age - stratuxClock.Since(mySituation.GPSLastGPSTimeStratuxTime).Seconds()) + 1
//if ti.ExtrapolatedPosition {
// timeDiff = math.Abs(ti.AgeExtrapolation - stratuxClock.Since(mySituation.GPSLastGPSTimeStratuxTime).Seconds()) + 1
//}
speed := mySituation.GPSGroundSpeed
if ti.Speed_valid {
speed = math.Max(float64(ti.Speed), mySituation.GPSGroundSpeed)
}
trafficDist := 0.0
if isGPSValid() {
trafficDist, _, _, _ = common.DistRect(float64(mySituation.GPSLatitude), float64(mySituation.GPSLongitude), float64(ti.Lat), float64(ti.Lng))
}
altDiff := 99999.0
if ti.AltIsGNSS && ti.Alt != 0 {
altDiff = math.Abs(float64(mySituation.GPSHeightAboveEllipsoid) - float64(ti.Alt))
} else if isTempPressValid() && ti.Alt != 0 {
altDiff = math.Abs(float64(mySituation.BaroPressureAltitude - float32(ti.Alt)))
} else {
// Cant verify relative altitude.. ignore it but don't use
shouldIgnore = true
continue
}
// Check if the distance to the ti is plausible
maxDistMetersIgnore := (timeDiff * speed * 0.514444 + float64(mySituation.GPSHorizontalAccuracy) + 50) * 2
if trafficDist > maxDistMetersIgnore {
log.Printf("Skipping ownship %s because it's too far away (%fm, speed=%f, max=%f)", ownCode, trafficDist, speed, maxDistMetersIgnore)
continue
}
// If we have a pressure sensor, and the pressure altitude of traffic and ownship is too big, skip...
if altDiff > 500 {
log.Printf("Skipping ownship %s because the altitude is off (%f ft)", ownCode, altDiff)
continue
}
// To really use the information from the ownship traffic info, we have much more
// strict requirements. At most 5s old and must be much closer
maxDistMetersOwnship := (timeDiff * speed * 0.514444 + float64(mySituation.GPSHorizontalAccuracy) + 20) * 1.4
if !isGPSValid() || (ti.Age <= 5 && trafficDist < maxDistMetersOwnship) && !ti.AltIsGNSS {
isOwnshipInfo = true
}
if globalSettings.DEBUG {
log.Printf("Using ownship %s. MaxDistIgnore: %f, maxDistOwnShip: %f, dist: %f, altDiff: %f, speed: %f, timeDiffS: %f, useForInfo: %t",
ownCode, maxDistMetersIgnore, maxDistMetersOwnship, trafficDist, altDiff, speed, timeDiff, isOwnshipInfo)
}
shouldIgnore = true
return
}
}
isOwnshipInfo = false
return
}
func sendTrafficUpdates() {
trafficMutex.Lock()
defer trafficMutex.Unlock()
cleanupOldEntries()
// Summarize number of UAT and 1090ES traffic targets for reports that follow.
globalStatus.UAT_traffic_targets_tracking = 0
globalStatus.ES_traffic_targets_tracking = 0
for _, traf := range traffic {
switch traf.Last_source {
case TRAFFIC_SOURCE_1090ES:
globalStatus.ES_traffic_targets_tracking++
case TRAFFIC_SOURCE_UAT:
globalStatus.UAT_traffic_targets_tracking++
}
}
var currAlt float32
currAlt = mySituation.BaroPressureAltitude
if currAlt == 99999 { // no valid BaroAlt, take GPS instead, better than nothing
currAlt = mySituation.GPSAltitudeMSL
}
var bestEstimate TrafficInfo
var highestAlarmLevel uint8
var highestAlarmTraffic TrafficInfo
if globalSettings.DEBUG && (stratuxClock.Time.Second()%15) == 0 {
log.Printf("List of all aircraft being tracked:\n")
log.Printf("==================================================================\n")
}
for key, ti := range traffic { // ForeFlight 7.5 chokes at ~1000-2000 messages depending on iDevice RAM. Practical limit likely around ~500 aircraft without filtering.
if isGPSValid() && ti.Position_valid {
// func distRect(lat1, lon1, lat2, lon2 float64) (dist, bearing, distN, distE float64) {
dist, bearing := common.Distance(float64(mySituation.GPSLatitude), float64(mySituation.GPSLongitude), float64(ti.Lat), float64(ti.Lng))
ti.Distance = dist
ti.Bearing = bearing
ti.BearingDist_valid = true
} else {
ti.Distance = 0
ti.Bearing = 0
ti.BearingDist_valid = false
}
ti.Age = stratuxClock.Since(ti.Last_seen).Seconds()
ti.AgeExtrapolation = stratuxClock.Since(ti.Last_extrapolation).Seconds()
ti.AgeLastAlt = stratuxClock.Since(ti.Last_alt).Seconds()
// Keep non-extrapolated traffic for 6 seconds, but extrapolate for 20
isCurrent := (ti.ExtrapolatedPosition && ti.AgeExtrapolation < 2 && ti.Age < 25) || (!ti.ExtrapolatedPosition && ti.Age < 6)
isOwnshipTi, shouldIgnore := isOwnshipTrafficInfo(ti)
// As bearingless targets, we show the closest estimated traffic that is between +-2000ft
if !shouldIgnore && !ti.Position_valid && ti.DistanceEstimated > 0 &&
(bestEstimate.DistanceEstimated == 0 || ti.DistanceEstimated < bestEstimate.DistanceEstimated) {
if ti.Alt != 0 && math.Abs(float64(ti.Alt) - float64(currAlt)) < 2000 {
bestEstimate = ti
}
}
// DEBUG: Print the list of all tracked targets (with data) to the log every 15 seconds if "DEBUG" option is enabled
if globalSettings.DEBUG && (stratuxClock.Time.Second()%15) == 0 {
s_out, err := json.Marshal(ti)
if err != nil {
log.Printf("Error generating output: %s\n", err.Error())
} else {
log.Printf("%X => %s\n", ti.Icao_addr, string(s_out))
}
// end of debug block
}
traffic[key] = ti // write the updated ti back to the map
//log.Printf("Traffic age of %X is %f seconds\n",icao,ti.Age)
if ti.Age > 2 { // if nothing polls an inactive ti, it won't push to the webUI, and its Age won't update.
trafficUpdate.SendJSON(ti)
}
if !shouldIgnore && isCurrent {
if float32(ti.Alt) <= currAlt + float32(globalSettings.RadarLimits) * 1.3 && //take 30% more to see moving outs
float32(ti.Alt) >= currAlt - float32(globalSettings.RadarLimits) * 1.3 && // altitude lower than upper boundary
(!ti.Position_valid || ti.Distance<float64(globalSettings.RadarRange) * 1852.0 * 1.3) { //allow more so that aircraft moves out
radarUpdate.SendJSON(ti)
}
}
if ti.Position_valid && isCurrent { // ... but don't pass stale data to the EFB.
//TODO: Coast old traffic? Need to determine how FF, WingX, etc deal with stale targets.
logTraffic(ti) // only add to the SQLite log if it's not stale
if isOwnshipTi {
if globalSettings.DEBUG {
log.Printf("Ownship target detected for code %X\n", ti.Icao_addr)
}
OwnshipTrafficInfo = ti
} else if !shouldIgnore {
priority := computeTrafficPriority(&ti)
sendGDL90(makeTrafficReportMsg(ti), time.Second, priority)
thisMsgFLARM, validFLARM, alarmLevel := makeFlarmPFLAAString(ti)
if alarmLevel > highestAlarmLevel {
highestAlarmLevel = alarmLevel
highestAlarmTraffic = ti
}
var trafficCallsign string
if len(ti.Tail) > 0 {
trafficCallsign = ti.Tail
} else {
trafficCallsign = fmt.Sprintf("%X_%d", ti.Icao_addr, ti.Squawk)
}
// send traffic message to X-Plane
sendXPlane(createXPlaneTrafficMsg(ti.Icao_addr, ti.Lat, ti.Lng, ti.Alt, uint32(ti.Speed), int32(ti.Vvel), ti.OnGround, uint32(ti.Track), trafficCallsign), 1000, priority)
if validFLARM {
sendNetFLARM(thisMsgFLARM, time.Second, priority)
}
}
}
}
// Also send the nearest best bearingless
if bestEstimate.DistanceEstimated > 0 && bestEstimate.DistanceEstimated < 15000 {
if isGPSValid() {
if globalSettings.EstimateBearinglessDist {
fakeTargets := calculateModeSFakeTargets(bestEstimate)
fakeMsg := make([]byte, 0)
for _, ti := range fakeTargets {
fakeMsg = append(fakeMsg, makeTrafficReportMsg(ti)...)
}
prio := computeTrafficPriority(&fakeTargets[0])
sendGDL90(fakeMsg, time.Second, prio)
}
prio := computeTrafficPriority(&bestEstimate)
msg, valid, _ := makeFlarmPFLAAString(bestEstimate)
if valid {
sendNetFLARM(msg, time.Second, prio)
}
}
}
msgPFLAU := makeFlarmPFLAUString(highestAlarmTraffic)
sendNetFLARM(msgPFLAU, time.Second, 0)
}
func computeTrafficPriority(ti *TrafficInfo) int32 {
if !ti.BearingDist_valid || ti.Alt == 0 {
return 9999999
}
var myAlt float32
if isTempPressValid() {
myAlt = mySituation.BaroPressureAltitude
} else {
myAlt = mySituation.GPSAltitudeMSL
}
altDiff := math.Abs(float64(myAlt) - float64(ti.Alt))
// assumes 333ft vertical difference has same priority 1000m horizontal
// This will usually produce priorities ranging from around 0-10
return int32((altDiff / 3.33 + ti.Distance) / 10000.0)
}
// Used to tune to our radios. We compare our estimate to real values for ADS-B Traffic.
// If we tend to estimate too high, we reduce this value, otherwise we increase it.
// We also try to correct for different transponder transmit power, by assuming that aircraft that fly high are bigger aircraft
// and have a stronger transponder. Low aircraft are small aircraft with weak transmission power.
// This is only a wild guess, but seems to help a bit. To do so, we use different estimatedDistFactors for different
// altitude buckets: <5000ft, 5000-10000ft, >10000ft
var estimatedDistFactors [3]float64 = [3]float64{2500.0, 2800.0, 3000.0}
func estimateDistance(ti *TrafficInfo) {
if ti.Last_source != TRAFFIC_SOURCE_1090ES {
return
}
altClass := int32(math.Max(0.0, math.Min(float64(ti.Alt / 5000), 2.0)))
dist := math.Pow(2.0, -ti.SignalLevel / 6.0) * estimatedDistFactors[altClass]; // distance approx. in meters, 6dB for double distance
lambda := 0.2;
timeDiff := ti.Timestamp.Sub(ti.DistanceEstimatedLastTs).Seconds() * 1000
ti.DistanceEstimatedLastTs = ti.Timestamp
if timeDiff < 0.0 {
return
}
expon := math.Exp(-timeDiff / 100 * lambda);
//log.Printf("timediff: %f, expon: %f", timeDiff, expon)
ti.DistanceEstimated = ti.DistanceEstimated * expon + dist * (1 - expon);
// Only learn from 1090ES ADS-B targets
// We ignore targets that are too far away (a lot of signal strength fluctuation), too close (non-reception cone or ownship)
// and of course extrapolated targets and invalid signal levels
if ti.BearingDist_valid && ti.Distance < 50000 && ti.Distance > 1500 && ti.Last_source == TRAFFIC_SOURCE_1090ES &&
ti.TargetType == TARGET_TYPE_ADSB && ti.SignalLevel > -30 && ti.SignalLevel < 0 && !ti.ExtrapolatedPosition {
var errorFactor float64
if ti.DistanceEstimated > ti.Distance {
errorFactor = -(ti.DistanceEstimated / ti.Distance)
} else {
errorFactor = ti.Distance / ti.DistanceEstimated
}
estimatedDistFactors[altClass] += errorFactor
//log.Printf("Estimate off: %f, new factor: %f", errorFactor, estimatedDistFactor)
if (estimatedDistFactors[altClass] < 1.0) {
estimatedDistFactors[altClass] = 1.0
}
}
}
// calculates coordinates of a point defined by a location, a bearing, and a distance, thanks to 0x74-0x62
func calcLocationForBearingDistance(lat1, lon1, bearingDeg, distanceNm float64) (lat2, lon2 float64) {
lat1Rad := common.Radians(lat1)
lon1Rad := common.Radians(lon1)
bearingRad := common.Radians(bearingDeg)
distanceRad := distanceNm / (180 * 60 / math.Pi)
lat2Rad := math.Asin(math.Sin(lat1Rad)*math.Cos(distanceRad) + math.Cos(lat1Rad)*math.Sin(distanceRad)*math.Cos(bearingRad))
distanceLon := -math.Atan2(math.Sin(bearingRad)*math.Sin(distanceRad)*math.Cos(lat1Rad), math.Cos(distanceRad)-math.Sin(lat1Rad)*math.Sin(lat2Rad))
lon2Rad := math.Mod(lon1Rad-distanceLon+math.Pi, 2.0*math.Pi) - math.Pi
lat2 = common.Degrees(lat2Rad)
lon2 = common.Degrees(lon2Rad)
return
}
func calculateModeSFakeTargets(bearinglessTi TrafficInfo) []TrafficInfo {
result := make([]TrafficInfo, 8)
for i := 0; i < 8; i++ {
ti := bearinglessTi
lat, lon := calcLocationForBearingDistance(float64(mySituation.GPSLatitude), float64(mySituation.GPSLongitude), float64(i * 45), bearinglessTi.DistanceEstimated / 1852.0)
ti.Lat = float32(lat)
ti.Lng = float32(lon)
ti.Icao_addr = uint32(i) // So that the EFB shows it as a different aircraft
ti.Speed = 0
ti.Speed_valid = true
ti.Tail = "MODE S"
result[i] = ti
}
return result
}
func postProcessTraffic(ti *TrafficInfo) {
ti.ReceivedMsgs += 1
estimateDistance(ti)
}
// Send update to attached JSON client.
func registerTrafficUpdate(ti TrafficInfo) {
//logTraffic(ti) // moved to sendTrafficUpdates() to reduce SQLite log size
/*
if !ti.Position_valid { // Don't send unless a valid position exists.
return
}
*/ // Send all traffic to the websocket and let JS sort it out. This will provide user indication of why they see 1000 ES messages and no traffic.
trafficUpdate.SendJSON(ti)
}
func isTrafficAlertable(ti TrafficInfo) bool {
// Set alert bit if possible and traffic is within some threshold
// TODO: Could be more intelligent, taking into account headings etc.
if !ti.BearingDist_valid {
// If not able to calculate the distance to the target, let the alert bit be set always.
return true
}
if ti.BearingDist_valid &&
ti.Distance < 3704 { // 3704 meters, 2 nm.
return true
}
return false
}
func makeTrafficReportMsg(ti TrafficInfo) []byte {
msg := make([]byte, 28)
// See p.16.
msg[0] = 0x14 // Message type "Traffic Report".
// Address type
msg[1] = ti.Addr_type
// Set alert if needed
if isTrafficAlertable(ti) {
// Set the alert bit. See pg. 18 of GDL90 ICD
msg[1] |= 0x10
}
// ICAO Address.
msg[2] = byte((ti.Icao_addr & 0x00FF0000) >> 16)
msg[3] = byte((ti.Icao_addr & 0x0000FF00) >> 8)
msg[4] = byte((ti.Icao_addr & 0x000000FF))
lat := float32(ti.Lat)
tmp := makeLatLng(lat)
msg[5] = tmp[0] // Latitude.
msg[6] = tmp[1] // Latitude.
msg[7] = tmp[2] // Latitude.
lng := float32(ti.Lng)
tmp = makeLatLng(lng)
msg[8] = tmp[0] // Longitude.
msg[9] = tmp[1] // Longitude.
msg[10] = tmp[2] // Longitude.
// Altitude: OK
// GDL 90 Data Interface Specification examples:
// where 1,000 foot offset and 25 foot resolution (1,000 / 25 = 40)
// -1,000 feet 0x000
// 0 feet 0x028
// +1000 feet 0x050
// +101,350 feet 0xFFE
// Invalid or unavailable 0xFFF
//
// Algo example at: https://play.golang.org/p/VXCckSdsvT
//
// GDL90 expects barometric altitude in traffic reports
var baroAlt int32
if ti.AltIsGNSS && isTempPressValid() {
// Convert from GPS geoid height to barometric altitude
baroAlt = ti.Alt - int32(mySituation.GPSGeoidSep)
baroAlt = baroAlt - int32(mySituation.GPSAltitudeMSL) + int32(mySituation.BaroPressureAltitude)
} else {
baroAlt = ti.Alt
}
var encodedAlt int16
if baroAlt < -1000 || baroAlt > 101350 {
encodedAlt = 0x0FFF
} else {
// output guaranteed to be between 0x0000 and 0x0FFE
encodedAlt = int16((baroAlt / 25) + 40)
}
msg[11] = byte((encodedAlt & 0xFF0) >> 4) // Altitude.
msg[12] = byte((encodedAlt & 0x00F) << 4)
// "m" field. Lower four bits define indicator bits:
// - - 0 0 "tt" (msg[17]) is not valid
// - - 0 1 "tt" is true track
// - - 1 0 "tt" is magnetic heading
// - - 1 1 "tt" is true heading
// - 0 - - Report is updated (current data)
// - 1 - - Report is extrapolated
// 0 - - - On ground
// 1 - - - Airborne
// Define tt type / validity
if ti.Speed_valid {
msg[12] = msg[12] | 0x01 // assume true track
}
if ti.ExtrapolatedPosition {
msg[12] = msg[12] | 0x04
}
if !ti.OnGround {
msg[12] = msg[12] | 0x08 // Airborne.
}
// Position containment / navigational accuracy
msg[13] = ((byte(ti.NIC) << 4) & 0xF0) | (byte(ti.NACp) & 0x0F)
// Horizontal velocity (speed).
msg[14] = byte((ti.Speed & 0x0FF0) >> 4)
msg[15] = byte((ti.Speed & 0x000F) << 4)
// Vertical velocity.
vvel := ti.Vvel / 64 // 64fpm resolution.
msg[15] = msg[15] | byte((vvel&0x0F00)>>8)
msg[16] = byte(vvel & 0x00FF)
// Track.
trk := uint8(ti.Track / TRACK_RESOLUTION) // Resolution is ~1.4 common.Degrees.
msg[17] = byte(trk)
msg[18] = ti.Emitter_category
// msg[19] to msg[26] are "call sign" (tail).
for i := 0; i < len(ti.Tail) && i < 8; i++ {
c := byte(ti.Tail[i])
if c != 0x20 && !((c >= 48) && (c <= 57)) && !((c >= 65) && (c <= 90)) && c != 'e' && c != 'u' && c != 'a' && c != 'r' && c != 't' { // See p.24, FAA ref.
c = byte(0x20)
}
msg[19+i] = c
}
//msg[27] is priority / emergency status per GDL90 spec (DO260B and DO282B are same codes)
msg[27] = ti.PriorityStatus << 4
return prepareMessage(msg)
}
// parseDownlinkReport decodes a UAT downlink message to extract identity, state vector, and mode status data.
// Decoded data is used to update a TrafficInfo object, keyed to the 24-bit ICAO code contained in the
// downlink message.
// Inputs are a checksum-verified hex string corresponding to the 18 or 34-byte UAT
// message, and an int representing UAT signal amplitude (0-1000).
func parseDownlinkReport(s string, signalLevel int) {
var ti TrafficInfo
s = s[1:]
frame := make([]byte, len(s)/2)
hex.Decode(frame, []byte(s))
// Extract header
msg_type := (uint8(frame[0]) >> 3) & 0x1f
addr_type := uint8(frame[0]) & 0x07
icao_addr := (uint32(frame[1]) << 16) | (uint32(frame[2]) << 8) | uint32(frame[3])
trafficMutex.Lock()
defer trafficMutex.Unlock()
// Retrieve previous information on this ICAO code.
if val, ok := traffic[icao_addr]; ok { // if we've already seen it, copy it in to do updates as it may contain some useful information like "tail" from 1090ES.
ti = val
//log.Printf("Existing target %X imported for UAT update\n", icao_addr)
} else {
//log.Printf("New target %X created for UAT update\n", icao_addr)
ti.Last_seen = stratuxClock.Time // need to initialize to current stratuxClock so it doesn't get cut before we have a chance to populate a position message
ti.Icao_addr = icao_addr
ti.ExtrapolatedPosition = false
thisReg, validReg := icao2reg(icao_addr)
if validReg {
ti.Reg = thisReg
ti.Tail = thisReg
}
}
ti.Addr_type = addr_type
var uat_version byte // sent as part of MS element, byte 24
// Extract parameters from Mode Status elements, if available.
if msg_type == 1 || msg_type == 3 {
// Determine UAT message version. This is needed for some capability decoding and is useful for debugging.
uat_version = (frame[23] >> 2) & 0x07
// Extract emitter category.
v := (uint16(frame[17]) << 8) | (uint16(frame[18]))
ti.Emitter_category = uint8((v / 1600) % 40)
// Decode callsign or Flight Plan ID (i.e. squawk code)
// If the CSID bit (byte 27, bit 7) is set to 1, all eight characters
// encoded in bytes 18-23 represent callsign.
// If the CSID bit is set to 0, the first four characters encoded in bytes 18-23
// represent the Mode A squawk code.
csid := (frame[26] >> 1) & 0x01
if csid == 1 { // decode as callsign
base40_alphabet := string("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ ..")
tail := ""
v := (uint16(frame[17]) << 8) | uint16(frame[18])
tail += string(base40_alphabet[(v/40)%40])
tail += string(base40_alphabet[v%40])
v = (uint16(frame[19]) << 8) | uint16(frame[20])
tail += string(base40_alphabet[(v/1600)%40])
tail += string(base40_alphabet[(v/40)%40])
tail += string(base40_alphabet[v%40])
v = (uint16(frame[21]) << 8) | uint16(frame[22])
tail += string(base40_alphabet[(v/1600)%40])
tail += string(base40_alphabet[(v/40)%40])
tail += string(base40_alphabet[v%40])
tail = strings.Trim(tail, " ")
ti.Tail = tail
} else if uat_version >= 2 { // decode as Mode 3/A code, if UAT version is at least 2
v := (uint16(frame[17]) << 8) | uint16(frame[18])
squawk_a := (v / 40) % 40
squawk_b := v % 40
v = (uint16(frame[19]) << 8) | uint16(frame[20])
squawk_c := (v / 1600) % 40
squawk_d := (v / 40) % 40
squawk := 1000*squawk_a + 100*squawk_b + 10*squawk_c + squawk_d
ti.Squawk = int(squawk)
}
ti.NACp = int((frame[25] >> 4) & 0x0F)
ti.PriorityStatus = (frame[23] >> 5) & 0x07
// Following section is future-use for debugging and / or additional status info on UAT traffic. Message parsing needs testing.
if globalSettings.DEBUG {
//declaration for mode status flags -- parse for debug logging
var status_sil byte
//var status_transmit_mso byte
var status_sda byte
var status_nacv byte
//var status_nicbaro byte
//var status_sil_supp byte
//var status_geom_vert_acc byte
//var status_sa_flag byte
var capability_uat_in bool
var capability_1090_in bool
//var capability_tcas bool
//var capability_cdti bool
//var opmode_tcas_active bool
//var opmode_ident_active bool
//var opmode_rec_atc_serv bool
// these are present in v1 and v2 messages
status_sil = frame[23] & 0x03
//status_transmit_mso = frame[24] >> 2
status_nacv = (frame[25] >> 1) & 0x07
//status_nicbaro = frame[25] & 0x01
// other status and capability bits are different between v1 and v2
if uat_version == 2 {
status_sda = frame[24] & 0x03
capability_uat_in = (frame[26] >> 7) != 0
capability_1090_in = ((frame[26] >> 6) & 0x01) != 0
//capability_tcas = ((frame[26] >> 5) & 0x01) != 0
//opmode_tcas_active = ((frame[26] >> 4) & 0x01) != 0
//opmode_ident_active = ((frame[26] >> 3) & 0x01) != 0
//opmode_rec_atc_serv = ((frame[26] >> 2) & 0x01) != 0
//status_sil_supp = frame[26] & 0x01
//status_geom_vert_acc = (frame[27] >> 6) & 0x03
//status_sa_flag = (frame[27] >> 5) & 0x01
} else if uat_version == 1 {
//capability_cdti = (frame[26] >> 7) != 0
//capability_tcas = ((frame[26] >> 6) & 0x01) != 0
//opmode_tcas_active = ((frame[26] >> 5) & 0x01) != 0
//opmode_ident_active = ((frame[26] >> 4) & 0x01) != 0
//opmode_rec_atc_serv = ((frame[26] >> 3) & 0x01) != 0
}
log.Printf("Supplemental UAT Mode Status for %06X: Version = %d; SIL = %d; SDA = %d; NACv = %d; 978 In = %v; 1090 In = %v\n", icao_addr, uat_version, status_sil, status_sda, status_nacv, capability_uat_in, capability_1090_in)
}
}
ti.NIC = int(frame[11] & 0x0F)
var power float64
if signalLevel > 0 {
power = 20 * (math.Log10(float64(signalLevel) / 1000)) // reported amplitude is 0-1000. Normalize to max = 1 and do amplitude dB calculation (20 dB per decade)
} else {
power = -999
}
//log.Printf("%s (%X) seen with amplitude of %d, corresponding to normalized power of %f.2 dB\n",ti.Tail,ti.Icao_addr,signalLevel,power)
ti.SignalLevel = power
if ti.Addr_type == 0 {
ti.TargetType = TARGET_TYPE_ADSB
} else if ti.Addr_type == 3 {
ti.TargetType = TARGET_TYPE_TISB
} else if ti.Addr_type == 6 {
ti.TargetType = TARGET_TYPE_ADSR
} else if ti.Addr_type == 2 {
ti.TargetType = TARGET_TYPE_TISB_S
if (ti.NIC >= 7) && (ti.Emitter_category > 0) { // If NIC is sufficiently high and emitter type is transmitted, we'll assume it's ADS-R.
ti.TargetType = TARGET_TYPE_ADSR
}
}
// This is a hack to show the source of the traffic on moving maps.
if globalSettings.DisplayTrafficSource {
type_code := " "
switch ti.TargetType {
case TARGET_TYPE_ADSB:
type_code = "a"
case TARGET_TYPE_ADSR, TARGET_TYPE_TISB_S:
type_code = "r"
case TARGET_TYPE_TISB:
type_code = "t"
}
if len(ti.Tail) == 0 {
ti.Tail = "u" + type_code
} else if len(ti.Tail) < 7 && ti.Tail[0] != 'e' && ti.Tail[0] != 'u' {
ti.Tail = "u" + type_code + ti.Tail
} else if len(ti.Tail) == 7 && ti.Tail[0] != 'e' && ti.Tail[0] != 'u' {
ti.Tail = "u" + type_code + ti.Tail[1:]
} else if len(ti.Tail) > 1 { // bounds checking
ti.Tail = "u" + type_code + ti.Tail[2:]
}
}
raw_lat := (uint32(frame[4]) << 15) | (uint32(frame[5]) << 7) | (uint32(frame[6]) >> 1)
raw_lon := ((uint32(frame[6]) & 0x01) << 23) | (uint32(frame[7]) << 15) | (uint32(frame[8]) << 7) | (uint32(frame[9]) >> 1)
lat := float32(0.0)
lng := float32(0.0)
position_valid := false
if /*(ti.NIC != 0) && */ (raw_lat != 0) && (raw_lon != 0) { // pass all traffic, and let the display determine if it will show NIC == 0. This will allow misconfigured or uncertified / portable emitters to be seen.
position_valid = true
lat = float32(raw_lat) * 360.0 / 16777216.0
if lat > 90 {
lat = lat - 180
}
lng = float32(raw_lon) * 360.0 / 16777216.0
if lng > 180 {
lng = lng - 360
}
}
ti.Position_valid = position_valid
if ti.Position_valid {
ti.Lat = lat
ti.Lng = lng
if isGPSValid() {
ti.Distance, ti.Bearing = common.Distance(float64(mySituation.GPSLatitude), float64(mySituation.GPSLongitude), float64(ti.Lat), float64(ti.Lng))
}
ti.Last_seen = stratuxClock.Time
ti.ExtrapolatedPosition = false
}
raw_alt := (int32(frame[10]) << 4) | ((int32(frame[11]) & 0xf0) >> 4)
alt_geo := false // Default case (i.e. 'false') is barometric
alt := int32(0)
if raw_alt != 0 {
alt_geo = (uint8(frame[9]) & 1) != 0
alt = ((raw_alt - 1) * 25) - 1000
}
ti.Alt = alt
ti.AltIsGNSS = alt_geo
ti.Last_alt = stratuxClock.Time
//OK.
// fmt.Printf("%d, %t, %f, %f, %t, %d\n", nic, position_valid, lat, lng, alt_geo, alt)
airground_state := (uint8(frame[12]) >> 6) & 0x03
//OK.
// fmt.Printf("%d\n", airground_state)
ns_vel := int32(0) // int16 won't work. Worst case (supersonic), we need 26 bits (25 bits + sign) for root sum of squares speed calculation
ew_vel := int32(0)
track := float32(0)
speed_valid := false
speed := uint16(0)
vvel := int16(0)
// vvel_geo := false
if airground_state == 0 || airground_state == 1 { // Subsonic. Supersonic.
ti.OnGround = false
// N/S velocity.
ns_vel_valid := false
ew_vel_valid := false
raw_ns := ((int16(frame[12]) & 0x1f) << 6) | ((int16(frame[13]) & 0xfc) >> 2)
if (raw_ns & 0x3ff) != 0 {
ns_vel_valid = true
ns_vel = int32((raw_ns & 0x3ff) - 1)
if (raw_ns & 0x400) != 0 {
ns_vel = 0 - ns_vel
}
if airground_state == 1 { // Supersonic.
ns_vel = ns_vel * 4
}
}
// E/W velocity.
raw_ew := ((int16(frame[13]) & 0x03) << 9) | (int16(frame[14]) << 1) | ((int16(frame[15] & 0x80)) >> 7)
if (raw_ew & 0x3ff) != 0 {
ew_vel_valid = true
ew_vel = int32((raw_ew & 0x3ff) - 1)
if (raw_ew & 0x400) != 0 {
ew_vel = 0 - ew_vel
}
if airground_state == 1 { // Supersonic.
ew_vel = ew_vel * 4
}
}
if ns_vel_valid && ew_vel_valid {
if ns_vel != 0 || ew_vel != 0 {
//TODO: Track type
track = float32((360 + 90 - (int16(math.Atan2(float64(ns_vel), float64(ew_vel)) * 180 / math.Pi))) % 360)
}
speed_valid = true
speed = uint16(math.Sqrt(float64((ns_vel * ns_vel) + (ew_vel * ew_vel))))
}
// Vertical velocity.
raw_vvel := ((int16(frame[15]) & 0x7f) << 4) | ((int16(frame[16]) & 0xf0) >> 4)
if (raw_vvel & 0x1ff) != 0 {
// vvel_geo = (raw_vvel & 0x400) == 0
vvel = ((raw_vvel & 0x1ff) - 1) * 64
if (raw_vvel & 0x200) != 0 {
vvel = 0 - vvel
}
}
} else if airground_state == 2 { // Ground vehicle.
ti.OnGround = true
raw_gs := ((uint16(frame[12]) & 0x1f) << 6) | ((uint16(frame[13]) & 0xfc) >> 2)
if raw_gs != 0 {
speed_valid = true
speed = ((raw_gs & 0x3ff) - 1)
}
raw_track := ((uint16(frame[13]) & 0x03) << 9) | (uint16(frame[14]) << 1) | ((uint16(frame[15]) & 0x80) >> 7)
//tt := ((raw_track & 0x0600) >> 9)
//FIXME: tt == 1 TT_TRACK. tt == 2 TT_MAG_HEADING. tt == 3 TT_TRUE_HEADING.
track = float32((raw_track & 0x1ff) * 360 / 512)
// Dimensions of vehicle - skip.
}
if msg_type == 1 || msg_type == 2 || msg_type == 5 || msg_type == 6 {
// Read AUXSV.
raw_alt := (int32(frame[29]) << 4) | ((int32(frame[30]) & 0xf0) >> 4)
if raw_alt != 0 {
alt := ((raw_alt - 1) * 25) - 1000
if ti.AltIsGNSS {
// Current ti.Alt is GNSS. Swap it for the AUXSV alt, which is baro.
baro_alt := ti.Alt
ti.Alt = alt
alt = baro_alt
ti.AltIsGNSS = false
}