diff --git a/LICENSE b/LICENSE
new file mode 100644
index 00000000..2ca453c6
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,26 @@
+Copyright (c) 2015 Christopher Young.
+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.
+    * Neither the name of the Joseph D Poirier nor the
+      names of its contributors may be used to endorse or promote products
+      derived from this software without specific prior written permission.
+
+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 <COPYRIGHT HOLDER> 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.
+
diff --git a/Makefile b/Makefile
new file mode 100644
index 00000000..c6ddb7ed
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,4 @@
+all:
+	GOARCH=6 go-linux-arm build gen_gdl90.go traffic.go ry835ai.go
+clean:
+	rm -f gen_gdl90
\ No newline at end of file
diff --git a/gen_gdl90.go b/gen_gdl90.go
index be07373d..a5d258f0 100644
--- a/gen_gdl90.go
+++ b/gen_gdl90.go
@@ -15,7 +15,7 @@ import (
 
 const (
 	stratuxVersion			= "v0.1"
-	configLocation			= "stratux.conf"
+	configLocation			= "/etc/stratux.conf"
 	ipadAddr                = "192.168.10.255:4000" // Port 4000 for FreeFlight RANGR.
 	maxDatagramSize         = 8192
 	UPLINK_BLOCK_DATA_BITS  = 576
@@ -39,11 +39,16 @@ const (
 
 	MSGCLASS_UAT		 = 0
 	MSGCLASS_ES			 = 1
+
+	LON_LAT_RESOLUTION	 = float32(180.0 / 8388608.0)
+	TRACK_RESOLUTION	 = float32(360.0 / 256.0)
 )
 
 var Crc16Table [256]uint16
 var outConn *net.UDPConn
 
+var myGPS GPSData
+
 type msg struct {
 	MessageClass	uint
 	TimeReceived	time.Time
@@ -103,18 +108,143 @@ func prepareMessage(data []byte) []byte {
 	return tmp
 }
 
+func makeLatLng(v float32) []byte {
+	ret := make([]byte, 3)
+
+	v = v / LON_LAT_RESOLUTION
+	wk := int32(v)
+
+	ret[0] = byte((wk & 0xFF0000) >> 16)
+	ret[1] = byte((wk & 0x00FF00) >> 8)
+	ret[2] = byte((wk & 0x0000FF))
+
+	return ret
+}
+
+func isGPSValid() bool {
+	return time.Since(myGPS.lastFixLocalTime).Seconds() < 15
+}
+
+func isGPSGroundTrackValid() bool {
+	return time.Since(myGPS.lastGroundTrackTime).Seconds() < 15
+}
+
+//TODO
+func makeOwnshipReport() bool {
+	if !isGPSValid() {
+		return false
+	}
+	msg := make([]byte, 28)
+	// See p.16.
+	msg[0] = 0x0A // Message type "Ownship".
+
+	msg[1] = 0x01 // Alert status, address type.
+
+	msg[2] = 1 // Address.
+	msg[3] = 1 // Address.
+	msg[4] = 1 // Address.
+
+	tmp := makeLatLng(myGPS.lat)
+	msg[5] = tmp[0] // Latitude.
+	msg[6] = tmp[1] // Latitude.
+	msg[7] = tmp[2] // Latitude.
+
+	tmp = makeLatLng(myGPS.lng)
+	msg[8] = tmp[0] // Longitude.
+	msg[9] = tmp[1] // Longitude.
+	msg[10] = tmp[2] // Longitude.
+
+
+//TODO: 0xFFF "invalid altitude."
+//FIXME: This is **PRESSURE ALTITUDE**
+
+	alt := uint16(myGPS.alt)
+	alt = (alt + 1000)/25
+	alt = alt & 0xFFF // Should fit in 12 bits.
+
+	msg[11] = byte((alt & 0xFF0) >> 4) // Altitude.
+	msg[12] = byte((alt & 0x00F) << 4)
+
+	if isGPSGroundTrackValid() {
+		msg[12] = byte(((alt & 0x00F) << 4) | 0xB) // "Airborne" + "True Heading"
+	} else {
+		msg[12] = byte((alt & 0x00F) << 4)
+	}
+	msg[13] = 0xBB // NIC and NACp.
+
+	gdSpeed := uint16(0) // 1kt resolution.
+	if isGPSGroundTrackValid() {
+		gdSpeed = myGPS.groundSpeed
+	}
+	gdSpeed = gdSpeed & 0x0FFF // Should fit in 12 bits.
+
+	msg[14] = byte((gdSpeed & 0xFF0) >> 4)
+	msg[15] = byte((gdSpeed & 0x00F) << 4)
+
+	verticalVelocity := int16(1000 / 64) // ft/min. 64 ft/min resolution.
+	//TODO: 0x800 = no information available.
+	verticalVelocity = verticalVelocity & 0x0FFF // Should fit in 12 bits.
+	msg[15] = msg[15] | byte((verticalVelocity & 0x0F00) >> 8)
+	msg[16] = byte(verticalVelocity & 0xFF)
+
+
+	// Showing magnetic (corrected) on ForeFlight. Needs to be True Heading.
+	groundTrack := uint16(0)
+	if isGPSGroundTrackValid() {
+		groundTrack = myGPS.trueCourse
+	}
+	trk := uint8(float32(groundTrack) / TRACK_RESOLUTION) // Resolution is ~1.4 degrees.
+
+	msg[17] = byte(trk)
+
+	msg[18] = 0x01 // "Light (ICAO) < 15,500 lbs"
+
+	outConn.Write(prepareMessage(msg))
+	return true
+}
+
+//TODO
+func makeOwnshipGeometricAltitudeReport() bool {
+	if !isGPSValid() {
+		return false
+	}
+	msg := make([]byte, 5)
+	// See p.28.
+	msg[0] = 0x0B // Message type "Ownship Geo Alt".
+	alt := int16(myGPS.alt)
+	alt = alt/5
+	msg[1] = byte(alt >> 8) // Altitude.
+	msg[2] = byte(alt & 0x00FF) // Altitude.
+
+	//TODO: "Figure of Merit". 0x7FFF "Not available".
+	msg[3] = 0x00
+	msg[4] = 0x0A
+
+	outConn.Write(prepareMessage(msg))
+	return true
+}
+
+func makeInitializationMessage() []byte {
+	msg := make([]byte, 3)
+	// See p.13.
+	msg[0] = 0x02 // Message type "Initialization".
+	msg[1] = 0x00 //TODO
+	msg[2] = 0x00 //TODO
+	return prepareMessage(msg)
+}
 
 func makeHeartbeat() []byte {
 	msg := make([]byte, 7)
 	// See p.10.
 	msg[0] = 0x00 // Message type "Heartbeat".
-	msg[1] = 0x01 // "UAT Initialized".
+	msg[1] = 0x01 // "UAT Initialized". //FIXME
+	msg[1] = 0x91 //FIXME: GPS valid. Addr talkback.
 	nowUTC := time.Now().UTC()
 	// Seconds since 0000Z.
 	midnightUTC := time.Date(nowUTC.Year(), nowUTC.Month(), nowUTC.Day(), 0, 0, 0, 0, time.UTC)
 	secondsSinceMidnightUTC := uint32(nowUTC.Sub(midnightUTC).Seconds())
 
-	msg[2] = byte((secondsSinceMidnightUTC >> 16) << 7)
+	msg[2] = byte(((secondsSinceMidnightUTC >> 16) << 7) | 0x1) // UTC OK.
 	msg[3] = byte((secondsSinceMidnightUTC & 0xFF))
 	msg[4] = byte((secondsSinceMidnightUTC & 0xFFFF) >> 8)
 
@@ -143,6 +273,12 @@ func relayMessage(msgtype uint16, msg []byte) {
 func heartBeatSender() {
 	for {
 		outConn.Write(makeHeartbeat())
+//		outConn.Write(makeTrafficReport())
+		makeOwnshipReport()
+		makeOwnshipGeometricAltitudeReport()
+		outConn.Write(makeInitializationMessage())
+		sendTrafficUpdates()
+		updateStatus()
 		time.Sleep(1 * time.Second)
 	}
 }
@@ -165,8 +301,13 @@ func updateStatus() {
 	MsgLog = t
 	globalStatus.UAT_messages_last_minute = UAT_messages_last_minute
 	globalStatus.ES_messages_last_minute = ES_messages_last_minute
+
+	if isGPSValid() {
+		globalStatus.GPS_satellites_locked = myGPS.satellites
+	}
 }
 
+
 func parseInput(buf string) ([]byte, uint16) {
 	x := strings.Split(buf, ";") // Discard everything after the first ';'.
 	if len(x) == 0 {
@@ -178,6 +319,10 @@ func parseInput(buf string) ([]byte, uint16) {
 	}
 	msgtype := uint16(0)
 
+	if s[0] == '-' {
+		parseDownlinkReport(s)
+	}
+
 	s = s[1:]
 	msglen := len(s) / 2
 
@@ -208,7 +353,6 @@ func parseInput(buf string) ([]byte, uint16) {
 	thisMsg.TimeReceived = time.Now()
 	thisMsg.Data = frame
 	MsgLog = append(MsgLog, thisMsg)
-	updateStatus()
 
 	return frame, msgtype
 }
@@ -216,6 +360,7 @@ func parseInput(buf string) ([]byte, uint16) {
 type settings struct {
 	UAT_Enabled					bool
 	ES_Enabled					bool
+	GPS_Enabled					bool
 }
 
 type status struct {
@@ -225,7 +370,7 @@ type status struct {
 	UAT_messages_max			uint
 	ES_messages_last_minute		uint
 	ES_messages_max				uint
-	GPS_satellites_locked		uint
+	GPS_satellites_locked		uint16
 }
 
 var globalSettings settings
@@ -257,6 +402,9 @@ func handleManagementConnection(conn net.Conn) {
 				fmt.Printf("%s - error: %s\n", s, err.Error())
 			} else {
 				fmt.Printf("new settings: %s\n", s)
+				if !globalSettings.GPS_Enabled && newSettings.GPS_Enabled { // GPS was enabled, restart the reader thread.
+					go gpsReader()
+				}
 				globalSettings = newSettings
 				saveSettings()
 			}
@@ -284,6 +432,7 @@ func managementInterface() {
 func defaultSettings() {
 	globalSettings.UAT_Enabled = true //TODO
 	globalSettings.ES_Enabled = false //TODO
+	globalSettings.GPS_Enabled = false //TODO
 }
 
 func readSettings() {
@@ -326,6 +475,10 @@ func saveSettings() {
 
 func main() {
 	MsgLog = make([]msg, 0)
+
+	crcInit() // Initialize CRC16 table.
+	initTraffic()
+
 	globalStatus.Version = stratuxVersion
 	globalStatus.Devices = 123 //TODO
 	globalStatus.UAT_messages_last_minute = 567 //TODO
@@ -333,7 +486,9 @@ func main() {
 
 	readSettings()
 
-	crcInit() // Initialize CRC16 table.
+	if globalSettings.GPS_Enabled {
+		go gpsReader()
+	}
 
 	// Open UDP port to send out the messages.
 	addr, err := net.ResolveUDPAddr("udp", ipadAddr)
diff --git a/image/spindle/wheezy-stage4 b/image/spindle/wheezy-stage4
index d368bf1f..85cbaa32 100755
--- a/image/spindle/wheezy-stage4
+++ b/image/spindle/wheezy-stage4
@@ -67,10 +67,6 @@ echo blacklist rtl2832 >>/etc/modprobe.d/rtl-sdr-blacklist.conf
 echo "# prevent power down of wireless when idle" >>/etc/modprobe.d/8192cu.conf
 echo "options 8192cu rtw_power_mgnt=0 rtw_enusbss=0" >>/etc/modprobe.d/8192cu.conf
 
-#usb hub power
-echo "max_usb_current=1" >>/boot/config.txt
-
-
 EOF
 
 echo "*** STRATUX COMPILE/PACKAGE INSTALL ***"
@@ -103,14 +99,12 @@ cp dump1090 /usr/bin/
 EOF
 
 echo " - Stratux"
+
+scp_in_to_qemu /root/spindle/gen_gdl90 /tmp/gen_gdl90
+
   ssh_in_to_qemu chroot /mnt sh -l -ex - <<\EOF
-apt-get install -y golang-go
 cd /root
 
-mkdir /root/go
-export GOPATH=/root/go
-
-
 rm -rf stratux
 git clone https://github.com/cyoung/stratux
 cd stratux
@@ -118,12 +112,9 @@ cd dump978
 make
 cp dump978 /usr/bin/
 cd ..
-go build gen_gdl90.go
 
-go get github.com/sevlyar/go-daemon
-go build 1090es_relay.go
-
-cp gen_gdl90 /usr/bin/
+mv /tmp/gen_gdl90 /usr/bin/gen_gdl90
+chmod +x /usr/bin/gen_gdl90
 cp start_uat.sh /usr/bin/start_uat
 cp init.d-stratux /etc/init.d/stratux
 cp start_stratux.sh /usr/sbin/stratux
@@ -132,7 +123,15 @@ chmod 755 /usr/sbin/stratux
 chmod 755 /etc/init.d/stratux
 ln -s /etc/init.d/stratux /etc/rc2.d/S01stratux
 ln -s /etc/init.d/stratux /etc/rc6.d/K01stratux
+
+echo -n '{"UAT_Enabled":false,"ES_Enabled":true,"GPS_Enabled":true}' >/etc/stratux.conf
+
 update-rc.d stratux enable
+
+#usb hub power
+echo "max_usb_current=1" >>/boot/config.txt
+
+
 EOF
 
 echo "**** END STRATUX SETUP *****"
diff --git a/ry835ai.go b/ry835ai.go
new file mode 100644
index 00000000..8379fb2f
--- /dev/null
+++ b/ry835ai.go
@@ -0,0 +1,186 @@
+package main
+
+
+import (
+	"fmt"
+	"github.com/tarm/serial"
+	"time"
+	"strings"
+	"strconv"
+)
+
+type GPSData struct {
+	lastFixSinceMidnightUTC uint32
+	lat float32
+	lng float32
+	quality uint8
+	satellites uint16
+	accuracy float32 // Meters.
+	alt float32 // Feet.
+	alt_accuracy float32
+	lastFixLocalTime time.Time
+	trueCourse uint16
+	groundSpeed uint16
+	lastGroundTrackTime time.Time
+}
+
+var serialConfig	*serial.Config
+var serialPort		*serial.Port
+
+func initGPSSerialReader() bool {
+	serialConfig = &serial.Config{Name: "/dev/ttyACM0", Baud: 9600}
+	p, err := serial.OpenPort(serialConfig)
+	if err != nil {
+		fmt.Printf("serial port err: %s\n", err.Error())
+		return false
+	}
+	serialPort = p
+	return true
+}
+
+func processNMEALine(l string) bool {
+	x := strings.Split(l, ",")
+	if x[0] == "$GNVTG" { // Ground track information.
+		if len(x) < 10 {
+			return false
+		}
+		trueCourse := uint16(0)
+		if len(x[1]) > 0 {
+			tc, err := strconv.ParseFloat(x[1], 32)
+			if err != nil {
+				return false
+			}
+			trueCourse = uint16(tc)
+		} else {
+			// No movement.
+			myGPS.trueCourse = 0
+			myGPS.groundSpeed = 0
+			myGPS.lastGroundTrackTime = time.Time{}
+			return true
+		}
+		groundSpeed, err := strconv.ParseFloat(x[5], 32) // Knots.
+		if err != nil {
+			return false
+		}
+
+		myGPS.trueCourse = uint16(trueCourse)
+		myGPS.groundSpeed = uint16(groundSpeed)
+		myGPS.lastGroundTrackTime = time.Now()
+	} else if x[0] == "$GNGGA" { // GPS fix.
+		if len(x) < 15 {
+			return false
+		}
+		var fix GPSData
+
+		fix = myGPS
+
+		// Timestamp.
+		if len(x[1]) < 9 {
+			return false
+		}
+		hr, err1 := strconv.Atoi(x[1][0:2])
+		min, err2 := strconv.Atoi(x[1][2:4])
+		sec, err3 := strconv.Atoi(x[1][4:6])
+		if err1 != nil || err2 != nil || err3 != nil {
+			return false
+		}
+
+		fix.lastFixSinceMidnightUTC = uint32((hr * 60 * 60) + (min * 60) + sec)
+
+		// Latitude.
+		if len(x[2]) < 10 {
+			return false
+		}
+		hr, err1 = strconv.Atoi(x[2][0:2])
+		minf, err2 := strconv.ParseFloat(x[2][2:10], 32)
+		if err1 != nil || err2 != nil {
+			return false
+		}
+
+		fix.lat = float32(hr) + float32(minf / 60.0)
+		if x[3] == "S" { // South = negative.
+			fix.lat = -fix.lat
+		}
+
+		// Longitude.
+		if len(x[4]) < 11 {
+			return false
+		}
+		hr, err1 = strconv.Atoi(x[4][0:3])
+		minf, err2 = strconv.ParseFloat(x[4][3:11], 32)
+		if err1 != nil || err2 != nil {
+			return false
+		}
+
+		fix.lng = float32(hr) + float32(minf / 60.0)
+		if x[5] == "W" { // West = negative.
+			fix.lng = -fix.lng
+		}
+
+		// Quality indicator.
+		q, err1 := strconv.Atoi(x[6])
+		if err1 != nil {
+			return false
+		}
+		fix.quality = uint8(q)
+
+		// Satellites.
+		sat, err1 := strconv.Atoi(x[7])
+		if err1 != nil {
+			return false
+		}
+		fix.satellites = uint16(sat)
+
+		// Accuracy.
+		hdop, err1 := strconv.ParseFloat(x[8], 32)
+		if err1 != nil {
+			return false
+		}
+		fix.accuracy = float32(hdop * 5.0) //FIXME: 5 meters ~ 1.0 HDOP?
+
+		// Altitude.
+		alt, err1 := strconv.ParseFloat(x[9], 32)
+		if err1 != nil {
+			return false
+		}
+		fix.alt = float32(alt * 3.28084) // Covnert to feet.
+
+		//TODO: Altitude accuracy.
+		fix.alt_accuracy = 0
+
+		// Timestamp.
+		fix.lastFixLocalTime = time.Now()
+
+		myGPS = fix
+
+	}
+	return true
+}
+
+func gpsSerialReader() {
+	defer serialPort.Close()
+	for {
+		if !globalSettings.GPS_Enabled { // GPS was turned off. Shut down.
+			break
+		}
+		buf := make([]byte, 1024)
+		n, err := serialPort.Read(buf)
+		if err != nil {
+			fmt.Printf("gps unit read error: %s\n", err.Error())
+			return
+		}
+		s := string(buf[:n])
+		x := strings.Split(s, "\n")
+		for _, l := range x {
+			processNMEALine(l)
+		}
+	}
+}
+
+func gpsReader() {
+	if initGPSSerialReader() {
+		gpsSerialReader()
+	} else {
+		globalSettings.GPS_Enabled = false
+	}
+}
\ No newline at end of file
diff --git a/traffic.go b/traffic.go
new file mode 100644
index 00000000..2a374bce
--- /dev/null
+++ b/traffic.go
@@ -0,0 +1,286 @@
+package main
+
+import (
+	"encoding/hex"
+	"math"
+	"time"
+)
+
+//-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
+
+*/
+
+type TrafficInfo struct {
+	icao_addr		uint32
+	addr_type 		uint8
+
+	lat				float32
+	lng				float32
+
+	position_valid	bool
+
+	alt				uint32
+
+	track			uint16
+	speed			uint16
+	speed_valid		bool
+
+	vvel			int16
+
+	tail			string
+
+	last_seen		time.Time
+}
+
+var traffic map[uint32]TrafficInfo
+
+func cleanupOldEntries() {
+	for icao_addr, ti := range traffic {
+		if time.Since(ti.last_seen).Seconds() > float64(60) { //FIXME: 60 seconds with no update on this address - stop displaying.
+			delete(traffic, icao_addr)
+		}
+	}
+}
+
+func sendTrafficUpdates() {
+	cleanupOldEntries()
+	for _, ti := range traffic {
+		makeTrafficReport(ti)
+	}
+}
+
+func initTraffic() {
+	traffic = make(map[uint32]TrafficInfo)
+}
+
+func makeTrafficReport(ti TrafficInfo) {
+	msg := make([]byte, 28)
+	// See p.16.
+	msg[0] = 0x14 // Message type "Traffic Report".
+
+	msg[1] = 0x10 | ti.addr_type // Alert status, address type.
+
+	// 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
+//TODO: 0xFFF "invalid altitude."
+	alt := uint16(ti.alt)
+	alt = (alt + 1000)/25
+	alt = alt & 0xFFF // Should fit in 12 bits.
+
+	msg[11] = byte((alt & 0xFF0) >> 4) // Altitude.
+	msg[12] = byte((alt & 0x00F) << 4)
+
+	msg[12] = byte(((alt & 0x00F) << 4) | 0x8) //FIXME. "Airborne".
+
+	msg[13] = 0x11 //FIXME.
+
+	// 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(float32(ti.track) / TRACK_RESOLUTION) // Resolution is ~1.4 degrees.
+	msg[17] = byte(trk)
+
+	msg[18] = 0x01 // "light"
+
+	outConn.Write(prepareMessage(msg))
+}
+
+
+func parseDownlinkReport(s string) {
+	var ti TrafficInfo
+	s = s[1:]
+	frame := make([]byte, len(s)/2)
+	hex.Decode(frame, []byte(s))
+
+	// Header.
+//	msg_type := (uint8(frame[0]) >> 3) & 0x1f
+	ti.addr_type = uint8(frame[0]) & 0x07
+	ti.icao_addr = (uint32(frame[1]) << 16) | (uint32(frame[2]) << 8) | uint32(frame[3])
+
+	// OK.
+//	fmt.Printf("%d, %d, %06X\n", msg_type, ti.addr_type, ti.icao_addr)
+
+	nic := uint8(frame[11]) & 15 //TODO: Meaning?
+
+	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 nic != 0 || raw_lat != 0 || raw_lon != 0 {
+		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.lat = lat
+	ti.lng = lng
+	ti.position_valid = position_valid
+
+	raw_alt := (uint32(frame[10]) << 4) | ((uint32(frame[11]) & 0xf0) >> 4)
+//	alt_geo := false // Barometric if not geometric.
+	alt := uint32(0)
+	if raw_alt != 0 {
+//		alt_geo = (uint8(frame[9]) & 1) != 0
+		alt = ((raw_alt - 1) * 25) - 1000
+	}
+	ti.alt = alt
+
+	//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 := int16(0)
+	ew_vel := int16(0)
+	track := uint16(0)
+	speed_valid := false
+	speed := uint16(0)
+	vvel := int16(0)
+//	vvel_geo := false
+	if airground_state == 0 || airground_state == 1 { // Subsonic. Supersonic.
+		// 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 = ((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 = (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 = (360 + 90 - uint16(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.
+		//TODO.
+		return
+	}
+
+	ti.track = track
+	ti.speed = speed
+	ti.vvel = vvel
+	ti.speed_valid = speed_valid
+
+	//OK.
+//	fmt.Printf("ns_vel %d, ew_vel %d, track %d, speed_valid %t, speed %d, vvel_geo %t, vvel %d\n", ns_vel, ew_vel, track, speed_valid, speed, vvel_geo, vvel)
+
+/*
+	utc_coupled := false
+	tisb_site_id := uint8(0)
+
+	if (uint8(frame[0]) & 7) == 2 || (uint8(frame[0]) & 7) == 3 { //TODO: Meaning?
+		tisb_site_id = uint8(frame[16]) & 0x0f
+	} else {
+		utc_coupled = (uint8(frame[16]) & 0x08) != 0
+	}
+*/
+
+	//OK.
+//	fmt.Printf("tisb_site_id %d, utc_coupled %t\n", tisb_site_id, utc_coupled)
+
+	ti.last_seen = time.Now()
+
+	traffic[ti.icao_addr] = ti
+}
\ No newline at end of file