Decode US civil Mode S codes to N numbers

2016-06-20 03:30:40 +00:00 · 2016-06-20 03:30:40 +00:00 · efaaa8777d
commit efaaa8777d
--- a/main/traffic.go
+++ b/main/traffic.go
@ -13,6 +13,7 @@ import (
 	"bufio"
 	"encoding/hex"
 	"encoding/json"
+	"fmt"
 	"log"
 	"math"
 	"net"
@ -75,7 +76,8 @@ const (

 type TrafficInfo struct {
 	Icao_addr           uint32
-	Tail                string
+	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.
 	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.
@ -349,6 +351,12 @@ func parseDownlinkReport(s string, signalLevel int) {
 		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 := icao2faa(icao_addr)
+		if validReg {
+			ti.Reg = thisReg
+			ti.Tail = thisReg
+		}
 	}

 	ti.Addr_type = addr_type
@ -650,6 +658,12 @@ func esListen() {
 				ti.Icao_addr = icao
 				ti.ExtrapolatedPosition = false
 				ti.Last_source = TRAFFIC_SOURCE_1090ES
+
+				thisReg, validReg := icao2faa(icao)
+				if validReg {
+					ti.Reg = thisReg
+					ti.Tail = thisReg
+				}
 			}

 			ti.SignalLevel = 10 * math.Log10(newTi.SignalLevel)
@ -1000,6 +1014,104 @@ func updateDemoTraffic(icao uint32, tail string, relAlt float32, gs float64, off
 	}
 }

+/*
+	icao2faa() : Converts 24-bit Mode S addresses to N-numbers.
+
+			Input: uint32 representing the Mode S address. Valid range for
+				translation is 0xA00001 - 0xADF7C7, inclusive.
+
+				Values outside the range A000001-AFFFFFF are flagged as non-US.
+				Values between ADF7C8 - AFFFFF are allocated to the United States,
+				but are not used for aicraft on the civil registry. These could be
+				military, other public aircraft, or (future use) temporary
+				anonymous addresses.
+
+			Output:
+				string: String containing the decoded tail number (if decoding succeeded),
+					"NON-US" (for non-US allocation), and "MIL" for non-civil US allocation.
+
+				bool: True if the Mode S address successfully translated to an
+					N number. False for all other conditions.
+*/
+
+func icao2faa(icao_addr uint32) (string, bool) {
+	// Initialize local variables
+	base34alphabet := string("ABCDEFGHJKLMNPQRSTUVWXYZ0123456789")
+	faaOffset := uint32(0xA00001)
+	tail := ""
+
+	// Discard non-US ICAO codes
+	if (icao_addr < 0xA00001) || (icao_addr > 0xAFFFFF) {
+		//fmt.Printf("%X is a non-US address.\n", icao_addr)
+		return "NON-US", false
+	}
+
+	// Discard addresses that are not assigned to aircraft on the civil registry (public aircraft: USAF, USN, USMC, USCG, ANG, FBI, etc.)
+	if icao_addr > 0xADF7C7 {
+		//fmt.Printf("%X is a US aircraft, but not on the civil registry.\n", icao_addr)
+		return "MIL", false
+	}
+
+	serial := int32(icao_addr - faaOffset)
+	// First digit
+	a := (serial / 101711) + 1
+
+	// Second digit
+	a_remainder := serial % 101711
+	b := ((a_remainder + 9510) / 10111) - 1
+
+	// Third digit
+	b_remainder := (a_remainder + 9510) % 10111
+	c := ((b_remainder + 350) / 951) - 1
+
+	// This next bit is more convoluted. First, figure out if we're using the "short" method of
+	// decoding the last two digits (two letters, one letter and one blank, or two blanks).
+	// This will be the case if digit "B" or "C" are calculated as negative, or if c_remainder
+	// is less than 601.
+
+	c_remainder := (b_remainder + 350) % 951
+	var d, e int32
+
+	if (b >= 0) && (c >= 0) && (c_remainder > 600) { // alphanumeric decoding method
+		d = 24 + (c_remainder-601)/35
+		e = (c_remainder - 601) % 35
+
+	} else { // two-letter decoding method
+		if (b < 0) || (c < 0) {
+			c_remainder -= 350 // otherwise "  " == 350, "A " == 351, "AA" == 352, etc.
+		}
+
+		d = (c_remainder - 1) / 25
+		e = (c_remainder - 1) % 25
+
+		if e < 0 {
+			d -= 1
+			e += 25
+		}
+	}
+
+	a_char := fmt.Sprintf("%d", a)
+	var b_char, c_char, d_char, e_char string
+
+	if b >= 0 {
+		b_char = fmt.Sprintf("%d", b)
+	}
+
+	if b >= 0 && c >= 0 {
+		c_char = fmt.Sprintf("%d", c)
+	}
+
+	if d > -1 {
+		d_char = string(base34alphabet[d])
+		if e > 0 {
+			e_char = string(base34alphabet[e-1])
+		}
+	}
+
+	tail = "N" + a_char + b_char + c_char + d_char + e_char
+	return tail, true
+}
+
 func initTraffic() {
 	traffic = make(map[uint32]TrafficInfo)
 	seenTraffic = make(map[uint32]bool)
--- a/web/plates/js/traffic.js
+++ b/web/plates/js/traffic.js
@ -59,6 +59,7 @@ function TrafficCtrl($rootScope, $scope, $state, $http, $interval) {
 		}
 		new_traffic.icao = obj.Icao_addr.toString(16).toUpperCase();
 		new_traffic.tail = obj.Tail;
+		new_traffic.reg = obj.Reg;
 		if (obj.Squawk == 0) {
 			new_traffic.squawk = "----";
 		} else {
--- a/web/plates/traffic.html
+++ b/web/plates/traffic.html
@ -9,7 +9,8 @@
 		<div class="panel-body traffic-page">
 			<div class="row">
 				<div class="col-sm-6">
-					<span class="col-xs-3"><strong>Callsign</strong></span>
+					<span class="col-xs-3" ng-hide="showReg"><strong>Callsign</strong></span>
+					<span class="col-xs-3" ng-show="showReg"><strong>Tail Num</strong></span>
 					<span class="col-xs-2" ng-hide="showSquawk"><strong>Code</strong></span>
 					<span class="col-xs-2" ng-show="showSquawk"><strong>Squawk</strong></span>
 					<span class="col-xs-5 text-right" ng-hide="GPS_connected && RelDist"><strong>Location</strong></span>
@ -29,11 +30,15 @@
 			<div class="row" ng-repeat="aircraft in data_list | orderBy: 'dist'">
 				<div class="separator"></div>
 				<div class="col-sm-6">
-					<span class="col-xs-3">
+					<span class="col-xs-3" ng-hide="showReg">
 						<span ng-show="aircraft.tail" ng-class="'label traffic-style'+aircraft.src+aircraft.targettype">{{aircraft.addr_symb}}<strong>&nbsp;{{aircraft.tail}}</strong></span>
 						<span ng-hide="aircraft.tail" ng-class="'label traffic-style'+aircraft.src+aircraft.targettype">{{aircraft.addr_symb}}<strong>&nbsp;[--N/A--]</strong></span>
+					</span>					
+					<span class="col-xs-3" ng-show="showReg">
+						<span ng-show="aircraft.reg" ng-class="'label traffic-style'+aircraft.src+aircraft.targettype">{{aircraft.addr_symb}}<strong>&nbsp;{{aircraft.reg}}</strong></span>
+						<span ng-hide="aircraft.reg" ng-class="'label traffic-style'+aircraft.src+aircraft.targettype">{{aircraft.addr_symb}}<strong>&nbsp;[--N/A--]</strong></span>
 					</span>
-				
+
 					<span class="col-xs-2">
 						<span style="font-size:80%" ng-hide="showSquawk">{{aircraft.icao}}<span style="font-size:50%">{{aircraft.addr_type == 3 ? "&nbsp;(TFID)" : ""}}</span></span>
 						<span ng-show="showSquawk"><span ng-show="aircraft.squawk < 1000">0</span><span ng-show="aircraft.squawk < 100">0</span><span ng-show="aircraft.squawk < 10">0</span>{{aircraft.squawk}}</span>
@ -60,19 +65,26 @@
 		<div class="panel-body traffic-footer">
 			<div class="separator"></div>
 			<div class="row">
+				<div class="col-sm-4">
+					<label class="control-label col-xs-6">Show Tail Number</label>
+					<span class="col-xs-3"><ui-switch ng-model='showReg' settings-change></ui-switch></span>
+				</div>
 				<div class="col-sm-4">
 					<label class="control-label col-xs-6">Show Squawk</label>
 					<span class="col-xs-3"><ui-switch ng-model='showSquawk' settings-change></ui-switch></span>
 				</div>
 				<div class="col-sm-4">
-					<label class="control-label col-xs-6">Show Distance</label>
+					<label class="control-label col-xs-6" ng-show="GPS_connected">Show Distance</label>
+					<label class="control-label text-muted col-xs-6" ng-hide="GPS_connected">Show Distance N/A</label>
 					<span class="col-xs-3"><ui-switch ng-model='RelDist' settings-change></ui-switch></span>
 				</div>
+				<!--
 				<div class="col-sm-4">
 					<label class="control-label col-xs-6">GPS Status</label>
 					<span ng-show="GPS_connected" class="label label-success col-xs-3" style="font-size:100%; display:block; height: 34px; line-height: 34px">Valid</span>
 					<span ng-hide="GPS_connected" class="label label-danger col-xs-3" style="font-size:100%; display:block; height: 34px; line-height: 34px">No Fix</span>
 				</div>
+				-->
 			</div>
 		</div>
 	</div>
@ -85,7 +97,8 @@
 		<div class="panel-body traffic-page">
 			<div class="row">
 				<div class="col-sm-6">
-					<span class="col-xs-4"><strong>Callsign</strong></span>
+					<span class="col-xs-4" ng-hide="showReg"><strong>Callsign</strong></span>
+					<span class="col-xs-4" ng-show="showReg"><strong>Tail Num</strong></span>
 					<span class="col-xs-3"><strong>Code</strong></span>
 					<span class="col-xs-3"><strong>Squawk</strong></span>
 				</div>
@ -102,9 +115,13 @@
 			<div class="row" ng-repeat="aircraft in data_list_invalid | orderBy: 'icao'">
 				<div class="separator"></div>
 				<div class="col-sm-6">
-					<span class="col-xs-4">
+					<span class="col-xs-4" ng-hide="showReg">
 						<span ng-show="aircraft.tail" ng-class="'label traffic-style'+aircraft.src+aircraft.targettype">{{aircraft.addr_symb}}<strong>&nbsp;{{aircraft.tail}}</strong></span>
 						<span ng-hide="aircraft.tail" ng-class="'label traffic-style'+aircraft.src+aircraft.targettype">{{aircraft.addr_symb}}<strong>&nbsp;[--N/A--]</strong></span>
+					</span>					
+					<span class="col-xs-4" ng-show="showReg">
+						<span ng-show="aircraft.reg" ng-class="'label traffic-style'+aircraft.src+aircraft.targettype">{{aircraft.addr_symb}}<strong>&nbsp;{{aircraft.reg}}</strong></span>
+						<span ng-hide="aircraft.reg" ng-class="'label traffic-style'+aircraft.src+aircraft.targettype">{{aircraft.addr_symb}}<strong>&nbsp;[--N/A--]</strong></span>
 					</span>
 					<span class="col-xs-3" style="font-size:80%">{{aircraft.icao}}<span style="font-size:50%">{{aircraft.addr_type == 3 ? "&nbsp;(TFID)" : ""}}</span></span>
 					<span class="col-xs-3"><span ng-show="aircraft.squawk < 1000">0</span><span ng-show="aircraft.squawk < 100">0</span><span ng-show="aircraft.squawk < 10">0</span>{{aircraft.squawk}}</span>