Initial import

2026-02-14 15:59:31 +01:00
parent 05dcea3c2b
commit f1ecbfaf8d
19 changed files with 2675 additions and 0 deletions
--- a/protocol/aprs/address.go
+++ b/protocol/aprs/address.go
@@ -0,0 +1,106 @@
+package aprs
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
+var (
+	ErrAddressInvalid = errors.New(`aprs: invalid address`)
+)
+
+type Address struct {
+	Call       string `json:"call"`
+	SSID       string `json:"ssid,omitempty"`
+	IsRepeated bool   `json:"is_repeated,omitempty"`
+}
+
+func (a Address) EqualTo(b Address) bool {
+	return a.Call == b.Call && a.SSID == b.SSID
+}
+
+func (a Address) String() string {
+	var r = ""
+
+	if a.IsRepeated {
+		r = "*"
+	}
+	if a.SSID == "" {
+		return a.Call + r
+	}
+	return fmt.Sprintf("%s-%s%s", a.Call, a.SSID, r)
+}
+
+func (a Address) Secret() int16 {
+	var h = int16(0x73e2)
+	var c = a.Call
+
+	if len(c)%2 > 0 {
+		c += "\x00"
+	}
+	for i := 0; i < len(c); i += 2 {
+		h ^= int16(c[i]) << 8
+		h ^= int16(c[i+1])
+	}
+	return h & 0x7fff
+}
+
+func ParseAddress(s string) (Address, error) {
+	r := strings.HasSuffix(s, "*")
+	if r {
+		s = s[:len(s)-1]
+	}
+	p := strings.Split(s, "-")
+	if len(p) == 0 || len(p) > 2 {
+		return Address{}, ErrAddressInvalid
+	}
+
+	a := Address{Call: p[0], IsRepeated: r}
+	if len(p) == 2 {
+		a.SSID = p[1]
+	}
+
+	return a, nil
+}
+
+func MustParseAddress(s string) Address {
+	a, err := ParseAddress(s)
+	if err != nil {
+		panic(err)
+	}
+	return a
+}
+
+func IsQConstruct(call string) bool {
+	return len(call) == 3 && call[0] == 'q'
+}
+
+type Path []Address
+
+func (p Path) String() string {
+	var s = make([]string, len(p))
+	for i, a := range p {
+		s[i] = a.String()
+	}
+	return strings.Join(s, ",")
+}
+
+func ParsePath(p string) (Path, error) {
+	ss := strings.Split(p, ",")
+
+	if len(ss) == 0 {
+		return nil, nil
+	}
+
+	var err error
+	as := make(Path, len(ss))
+	for i, s := range ss {
+		as[i], err = ParseAddress(s)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return as, nil
+}
--- a/protocol/aprs/base91.go
+++ b/protocol/aprs/base91.go
@@ -0,0 +1,29 @@
+package aprs
+
+import (
+	"fmt"
+	"strings"
+)
+
+func base91Decode(s string) (n int, err error) {
+	for i, l := 0, len(s); i < l; i++ {
+		c := s[i]
+		if c < 33 || c > 122 {
+			return 0, fmt.Errorf("aprs: invalid base-91 encoding char %q (%d)", c, c)
+		}
+
+		n *= 91
+		n += int(c) - 33
+	}
+	return
+}
+
+func base91Encode(n int) string {
+	var s []string
+	for n > 0 {
+		c := n % 91
+		n /= 91
+		s = append([]string{string(byte(c) + 33)}, s...)
+	}
+	return strings.Join(s, "")
+}
--- a/protocol/aprs/datatype.go
+++ b/protocol/aprs/datatype.go
@@ -0,0 +1,41 @@
+package aprs
+
+import "fmt"
+
+type DataType byte
+
+var (
+	dataTypeName = map[DataType]string{
+		0x1c: "Current Mic-E Data (Rev 0 beta)",
+		0x1d: "Old Mic-E Data (Rev 0 beta)",
+		'!':  "Position without timestamp (no APRS messaging), or Ultimeter 2000 WX Station",
+		'#':  "Peet Bros U-II Weather Station",
+		'$':  "Raw GPS data or Ultimeter 2000",
+		'%':  "Agrelo DFJr / MicroFinder",
+		'"':  "Old Mic-E Data (but Current data for TM-D700)",
+		')':  "Item",
+		'*':  "Peet Bros U-II Weather Station",
+		',':  "Invalid data or test data",
+		'/':  "Position with timestamp (no APRS messaging)",
+		':':  "Message",
+		';':  "Object",
+		'<':  "Station Capabilities",
+		'=':  "Position without timestamp (with APRS messaging)",
+		'>':  "Status",
+		'?':  "Query",
+		'@':  "Position with timestamp (with APRS messaging)",
+		'T':  "Telemetry data",
+		'[':  "Maidenhead grid locator beacon (obsolete)",
+		'_':  "Weather Report (without position)",
+		'`':  "Current Mic-E Data (not used in TM-D700)",
+		'{':  "User-Defined APRS packet format",
+		'}':  "Third-party traffic",
+	}
+)
+
+func (t DataType) String() string {
+	if s, ok := dataTypeName[t]; ok {
+		return s
+	}
+	return fmt.Sprintf("Unknown packet type %#02x", byte(t))
+}
--- a/protocol/aprs/doc.go
+++ b/protocol/aprs/doc.go
@@ -0,0 +1,2 @@
+// Package aprs implements Automatic Packet Reporting System message parsing.
+package aprs
--- a/protocol/aprs/packet.go
+++ b/protocol/aprs/packet.go
@@ -0,0 +1,481 @@
+package aprs
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var (
+	// ErrInvalidPacket signals a corrupted/unknown APRS packet.
+	ErrInvalidPacket = errors.New("aprs: invalid packet")
+
+	// ErrInvalidPosition signals a corrupted APRS position report.
+	ErrInvalidPosition = errors.New("aprs: invalid position")
+)
+
+// Payload is the raw payload contained within an APRS packet.
+type Payload string
+
+// Type of payload.
+func (p Payload) Type() DataType {
+	var t DataType
+
+	if len(p) > 0 {
+		t = DataType(p[0])
+	}
+
+	return t
+}
+
+func isDigit(b byte) bool {
+	return b >= '0' && b <= '9'
+}
+
+func (p Payload) Len() int { return len(p) }
+
+// Velocity details.
+type Velocity struct {
+	Course float64 // Degrees
+	Speed  float64 // Knots
+}
+
+// Wind details.
+type Wind struct {
+	Direction float64 // Degrees
+	Speed     float64 // Knots
+}
+
+// PowerHeightGain details.
+type PowerHeightGain struct {
+	PowerCode       byte
+	HeightCode      byte
+	GainCode        byte
+	DirectivityCode byte
+}
+
+// Power level (in Watts).
+func (p PowerHeightGain) Power() int {
+	w := int(p.PowerCode - '0')
+	if w <= 0 {
+		return 0
+	}
+	return w * w
+}
+
+// Height above ground (in meters).
+func (p PowerHeightGain) Height() float64 {
+	h := float64(p.HeightCode - '0')
+	if h <= 0 {
+		return 10
+	}
+	return math.Pow(2, h) * 10
+}
+
+// Gain level (in dBs).
+func (p PowerHeightGain) Gain() int {
+	d := int(p.GainCode - '0')
+	if d <= 0 {
+		return 0
+	}
+	return d
+}
+
+// Directivity angle.
+func (p PowerHeightGain) Directivity() float64 {
+	d := int(p.DirectivityCode - '0')
+	if d <= 0 {
+		return 0
+	}
+	return float64(d%8) * 45.0
+}
+
+// OmniDFStrength contains the omni-directional direction finding signal strength (for fox hunting).
+type OmniDFStrength struct {
+	StrengthCode    byte
+	HeightCode      byte
+	GainCode        byte
+	DirectivityCode byte
+}
+
+// Strength of the signal.
+func (o OmniDFStrength) Strength() int {
+	w := int(o.StrengthCode - '0')
+	if w <= 0 {
+		return 0
+	}
+	return w * w
+}
+
+// Height above ground (in meters).
+func (o OmniDFStrength) Height() float64 {
+	h := float64(o.HeightCode - '0')
+	if h <= 0 {
+		return 10
+	}
+	return math.Pow(2, h) * 10
+}
+
+// Gain level (in dBs).
+func (o OmniDFStrength) Gain() int {
+	d := int(o.GainCode - '0')
+	if d <= 0 {
+		return 0
+	}
+	return d
+}
+
+// Directivity angle.
+func (o OmniDFStrength) Directivity() float64 {
+	d := int(o.DirectivityCode - '0')
+	if d <= 0 {
+		return 0
+	}
+	return float64(d%8) * 45.0
+}
+
+// Packet contains an APRS packet.
+type Packet struct {
+	// Raw packet (as captured from the air or APRS-IS).
+	Raw string `json:"raw"`
+
+	// Src is the source address.
+	Src Address `json:"src"`
+
+	// Dst is the destination address.
+	Dst Address `json:"dst"`
+
+	// Path contains the digipeater path.
+	Path Path `json:"path,omitempty"`
+
+	// Payload is the raw payload.
+	Payload Payload `json:"payload"`
+
+	// Position encoded in the payload.
+	Position *Position `json:"position,omitempty"`
+
+	// Time encoded in the payload.
+	Time *time.Time `json:"time,omitempty"`
+
+	// Altitude encoded in the payload (in feet).
+	Altitude float64 `json:"altitude,omitempty"`
+
+	// Velocity encoded in the payload.
+	Velocity *Velocity `json:"velocity,omitempty"`
+
+	// Wind details encoded in the payload.
+	Wind *Wind `json:"wind,omitempty"`
+
+	// PHG are the power, height and gain details encoded in the payload.
+	PHG *PowerHeightGain `json:"phg,omitempty"`
+
+	// DFS are the direction finder strength details encoded in the payload.
+	DFS *OmniDFStrength `json:"dfs,omitempty"`
+
+	// Range encoded in the payload (in miles).
+	Range float64 `json:"range,omitempty"`
+
+	// Symbol encoded in the payload.
+	Symbol Symbol `json:"symbol"`
+
+	// Comment encoded in the payload.
+	Comment string `json:"comment,omitempty"`
+
+	// Unparsed data.
+	data string
+}
+
+// ParsePacket parses an APRS packet as captured from AX.25 or APRS-IS.
+func ParsePacket(raw string) (Packet, error) {
+	p := Packet{Raw: raw}
+
+	var i int
+	if i = strings.Index(raw, ":"); i < 0 {
+		return p, ErrInvalidPacket
+	}
+	p.Payload = Payload(raw[i+1:])
+
+	// Parse src, dst and path
+	var err error
+	var a = raw[:i]
+	if i = strings.Index(a, ">"); i < 0 {
+		return p, ErrInvalidPacket
+	}
+	if p.Src, err = ParseAddress(a[:i]); err != nil {
+		return p, err
+	}
+	var r = strings.Split(a[i+1:], ",")
+	if p.Dst, err = ParseAddress(r[0]); err != nil {
+		return p, err
+	}
+	if p.Path, err = ParsePath(strings.Join(r[1:], ",")); err != nil {
+		return p, err
+	}
+
+	// Post processing of payload
+	err = p.parse()
+	return p, err
+}
+
+func (p *Packet) parse() error {
+	s := string(p.Payload)
+	//log.Printf("parse %q [%c]\n", s, p.Payload.Type())
+
+	switch p.Payload.Type() {
+	case '!': // Lat/Long Position Report Format — without Timestamp
+		var o = strings.IndexByte(s, '!')
+		pos, txt, err := ParsePosition(s[o+1:], !isDigit(s[o+1]))
+		if err != nil {
+			return err
+		}
+		p.Position = &pos
+		p.data = txt
+		if len(s) >= 20 {
+			p.Symbol[0] = s[9]
+			p.Symbol[1] = s[19]
+		}
+	case '=':
+		compressed := IsValidCompressedSymTable(s[1])
+		pos, txt, err := ParsePosition(s[1:], compressed)
+		if err != nil {
+			return err
+		}
+		p.Position = &pos
+		p.data = txt
+		if compressed {
+			p.Symbol[0] = s[1]
+			p.Symbol[1] = s[10]
+		} else {
+			p.Symbol[0] = s[9]
+			p.Symbol[1] = s[19]
+		}
+	case '/', '@': // Lat/Long Position Report Format — with Timestamp
+		if len(s) < 8 {
+			return ErrInvalidPosition
+		}
+
+		var compressed bool
+		if s[7] == 'h' || s[7] == 'z' || s[7] == '/' {
+			if ts, err := ParseTime(s[1:]); err == nil {
+				p.Time = &ts
+			}
+			compressed = IsValidCompressedSymTable(s[8])
+			pos, txt, err := ParsePosition(s[8:], compressed)
+			if err != nil {
+				return err
+			}
+			p.Position = &pos
+			p.data = txt
+		} else if s[7] >= '0' && s[7] <= '9' {
+			ts, err := ParseTime(s[1:])
+			if err != nil {
+				return err
+			}
+			p.Time = &ts
+			compressed = IsValidCompressedSymTable(s[10])
+			pos, txt, err := ParsePosition(s[10:], compressed)
+			if err != nil {
+				return err
+			}
+			p.Position = &pos
+			p.data = txt
+		}
+		if compressed {
+			p.Symbol[0] = s[8]
+			p.Symbol[1] = s[17]
+		} else {
+			p.Symbol[0] = s[16]
+			p.Symbol[1] = s[26]
+		}
+	case ';':
+		pos, txt, err := ParsePosition(s[18:], !isDigit(s[18]))
+		if err != nil {
+			return err
+		}
+		p.Position = &pos
+		p.data = txt
+	case '[':
+		pos, txt, err := ParsePositionGrid(s[1:])
+		if err != nil {
+			return err
+		}
+		p.Position = &pos
+		p.data = txt
+	case '`', '\'':
+		pos, err := ParseMicE(s, p.Dst.Call)
+		if err != nil {
+			return err
+		}
+		p.Position = &pos
+		p.parseMicEData()
+
+		return nil // there is no additional data to parse
+	default:
+		pos, txt, err := ParsePositionBoth(s)
+		if err != nil {
+			if err != ErrInvalidPosition {
+				return err
+			}
+			p.Comment = s[1:]
+		} else {
+			p.Position = &pos
+			p.Comment = txt
+		}
+	}
+
+	if p.Position != nil {
+		if p.Position.Compressed {
+			return p.parseCompressedData()
+		}
+		return p.parseData()
+	}
+
+	return nil
+}
+
+func (p *Packet) parseMicEData() error {
+	// APRS PROTOCOL REFERENCE 1.0.1 Chapter 10, page 42 in PDF
+
+	s := string(p.Payload)
+
+	// Mic-E Message Type
+	var mt []string
+	var t string
+	for i := 0; i < 3; i++ {
+		mc := miceCodes[rune(p.Dst.Call[i])][1]
+		if strings.HasSuffix(mc, "(Custom)") {
+			t = messageTypeCustom
+		} else if strings.HasSuffix(mc, "(Std)") {
+			t = messageTypeStd
+		}
+		mt = append(mt, string(mc[0]))
+	}
+	switch t {
+	case messageTypeStd:
+		mt = append(mt, " (Std)")
+	case messageTypeCustom:
+		mt = append(mt, " (Custom)")
+	}
+	p.Comment = miceMsgTypes[strings.Join(mt, "")]
+
+	// Speed and Course.
+	speed := float64(int(s[4])-28) * 10
+	dc := float64(int(s[5])-28) / 10
+	unit := float64(int(dc))
+	speed += unit
+	course := dc - unit
+	course += float64(int(s[6]) - 28)
+	if speed >= 800 {
+		speed -= 800
+	}
+	speed = 1.852 * speed // convert speed from knots to km/h
+	if course >= 400 {
+		course -= 400
+	}
+
+	// Symbol
+	p.Symbol[0] = s[7]
+	p.Symbol[1] = s[8]
+
+	p.Comment += fmt.Sprintf(" (%.fkm/h, %.f°)", speed, course)
+
+	// Check whether there's additional Telemetry or Status Text data.
+	if len(s) == 9 {
+		return nil
+	}
+
+	if s[9] == ',' || s[9] == '\x1d' {
+		// TODO: Parse telemetry data.
+		return nil
+	}
+
+	// Parse MicE Status Text data.
+	// TODO: Parse additional data in the Status Text data:
+	// - Actual (custom) text message
+	// - Maidenhead locator
+	// - Altitude
+
+	return nil
+}
+
+func (p *Packet) parseCompressedData() error {
+	// Parse csT bytes
+	if len(p.data) >= 3 {
+		// Compression Type (T) Byte Format
+		// Bit: 7      | 6      | 5       | 4     3     | 2    1    0      |
+		//	-------+--------+---------+-------------+------------------+
+		//      Unused | Unused | GPS Fix | NMEA Source | Origin           |
+		//	-------+--------+---------+-------------+------------------+
+		// Val: 0      | 0      | 0 = old | 00 = other  | 000 = Compressed |
+		//	       |        | 1 = cur | 01 = GLL    | 001 = TNC BTex   |
+		//	       |        |         | 10 = CGA    | 010 = Software   |
+		//	       |        |         | 11 = RMC    | 011 = [tbd]      |
+		//	       |        |         |             | 100 = KPC3       |
+		//	       |        |         |             | 101 = Pico       |
+		//	       |        |         |             | 110 = Other      |
+		//	       |        |         |             | 111 = Digipeater |
+		cb := p.data[0] - 33
+		sb := p.data[1] - 33
+		Tb := p.data[2] - 33
+		if p.data[0] != ' ' && ((Tb>>3)&3) == 2 {
+			// CGA sentence, NMEA Source = 0b10
+			d, err := base91Decode(p.data[0:2])
+			if err != nil {
+				return err
+			}
+			p.Altitude = math.Pow(1.002, float64(d))
+			p.Comment = p.data[3:]
+		} else if cb <= 89 { // !..z
+			// Course/Speed
+			p.Velocity.Course = float64(cb) * 4.0
+			p.Velocity.Speed = math.Pow(1.08, float64(sb)) - 1.0
+		} else if cb == 90 { // {
+			// Pre-Calculated Radio Range
+			p.Range = 2 * math.Pow(1.08, float64(sb))
+		}
+	}
+	return nil
+}
+
+func (p *Packet) parseData() error {
+	switch {
+	case len(p.data) >= 1 && p.data[0] == ' ':
+		p.Comment = p.data[1:]
+
+	case len(p.data) >= 7 && strings.HasPrefix(p.data, "PHG"):
+		p.PHG.PowerCode = p.data[3]
+		p.PHG.HeightCode = p.data[4]
+		p.PHG.GainCode = p.data[5]
+		p.PHG.DirectivityCode = p.data[6]
+		p.Range = math.Sqrt(2 * p.PHG.Height() * math.Sqrt((float64(p.PHG.Power())/10)*(float64(p.PHG.Gain())/2)))
+		p.Comment = p.data[7:]
+
+	case len(p.data) >= 7 && strings.HasPrefix(p.data, "RNG"):
+		var err error
+		p.Range, err = strconv.ParseFloat(p.data[3:7], 64)
+		if err != nil {
+			return err
+		}
+		p.Comment = p.data[7:]
+
+	case len(p.data) >= 7 && strings.HasPrefix(p.data, "DFS"):
+		p.DFS.StrengthCode = p.data[3]
+		p.DFS.HeightCode = p.data[4]
+		p.DFS.GainCode = p.data[5]
+		p.DFS.DirectivityCode = p.data[6]
+		p.Comment = p.data[7:]
+	}
+	return nil
+}
+
+func (p Payload) Time() (time.Time, error) {
+	switch p.Type() {
+	case '/', '@':
+		return ParseTime(string(p)[1:])
+	default:
+		return time.Time{}, nil
+	}
+}
--- a/protocol/aprs/packet_test.go
+++ b/protocol/aprs/packet_test.go
@@ -0,0 +1,329 @@
+package aprs
+
+import (
+	"math"
+	"testing"
+	"time"
+)
+
+const earthRadius = float64(6378100)
+
+func testTime(day, hour, min, sec int) *time.Time {
+	t := time.Date(0, 0, day, hour, min, sec, 0, time.UTC)
+	return &t
+}
+
+// haversin(θ) function
+func testHaversin(theta float64) float64 {
+	return math.Pow(math.Sin(theta/2), 2)
+}
+
+func testDistance(a *Position, b *Position) float64 {
+	var (
+		lat1 = a.Latitude * math.Pi / 180
+		lng1 = a.Longitude * math.Pi / 180
+		lat2 = b.Latitude * math.Pi / 180
+		lng2 = b.Longitude * math.Pi / 180
+		h    = testHaversin(lat2-lat1) + math.Cos(lat1)*math.Cos(lat2)*testHaversin(lng2-lng1)
+	)
+	return 2 * earthRadius * math.Asin(math.Sqrt(h))
+}
+
+func TestPacket(t *testing.T) {
+	var tests = []struct {
+		Raw      string
+		Src      Address
+		Dst      Address
+		PathLen  int
+		Type     DataType
+		Position *Position
+		Velocity *Velocity
+		PHG      *PowerHeightGain
+		DFS      *OmniDFStrength
+		Altitude float64
+		Range    float64
+		Time     *time.Time
+	}{
+		{
+			Raw:      "N0CALL>APRS,qAC:!4903.50N/07201.75W-Test 001234",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('!'),
+			Position: &Position{Latitude: 49.058333, Longitude: -72.029167},
+		},
+		{
+			Raw:      "N0CALL>APRS,qAC:!4903.50N/07201.75W-Test /A=001234",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('!'),
+			Position: &Position{Latitude: 49.058333, Longitude: -72.029167},
+		},
+		{
+			Raw:      "N0CALL>APRS,qAC:!49  .  N/072  .  W-",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('!'),
+			Position: &Position{Latitude: 49.0, Longitude: -72.000000},
+		},
+		/*
+			{
+				Raw:      "N0CALL>APRS,qAC:TheNet X-1J4  (BFLD)!4903.50N/07201.75Wn",
+				Src:      MustParseAddress("N0CALL"),
+				Dst:      MustParseAddress("APRS"),
+				PathLen:  1,
+				Type:     DataType('!'),
+				Position: &Position{Latitude: 49.058333, Longitude: -72.029167},
+			},
+		*/
+		{
+			Raw:      "N0CALL>APRS,qAC:@092345/4903.50N/07201.75W>Test1234",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('@'),
+			Position: &Position{Latitude: 49.058333, Longitude: -72.029167},
+			Time:     testTime(9, 23, 45, 0),
+		},
+		{
+			Raw:      "N0CALL>APRS,qAC:=4903.50N/07201.75W#PHG5132",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('='),
+			Position: &Position{Latitude: 49.058333, Longitude: -72.029167},
+			PHG:      &PowerHeightGain{'5', '1', '3', '2'},
+		},
+		{
+			Raw:      "N0CALL>APRS,qAC:=4903.50N/07201.75W 225/000g000t050r000p001...h00b10138dU2k",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('='),
+			Position: &Position{Latitude: 49.058333, Longitude: -72.029167},
+		},
+		{
+			Raw:      "N0CALL>APRS,qAC:@092345/4903.50N/07201.75W>088/036",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('@'),
+			Position: &Position{Latitude: 49.058333, Longitude: -72.029167},
+			Time:     testTime(9, 23, 45, 0),
+		},
+		{
+			Raw:      "N0CALL>APRS,qAC:@234517h4903.50N/07201.75W>PHG5132",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('@'),
+			Position: &Position{Latitude: 49.058333, Longitude: -72.029167},
+			Time:     testTime(0, 23, 45, 17),
+			PHG:      &PowerHeightGain{'5', '1', '3', '2'},
+		},
+		{
+			Raw:      "N0CALL>APRS,qAC:@092345z4903.50N/07201.75W>RNG0050",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('@'),
+			Position: &Position{Latitude: 49.058333, Longitude: -72.029167},
+			Time:     testTime(9, 23, 45, 0),
+			Range:    50,
+		},
+		{
+			Raw:      "N0CALL>APRS,qAC:/234517h4903.50N/07201.75W>DFS2360",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('/'),
+			Position: &Position{Latitude: 49.058333, Longitude: -72.029167},
+			Time:     testTime(0, 23, 45, 17),
+			DFS:      &OmniDFStrength{'2', '3', '6', '0'},
+		},
+		{
+			Raw:      "N0CALL>APRS,qAC:@092345z4903.50N/07201.75W 090/000g000t066r000p000...dUII",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('@'),
+			Position: &Position{Latitude: 49.058333, Longitude: -72.029167},
+			Time:     testTime(9, 23, 45, 00),
+		},
+		{
+			Raw:      "N0CALL>APRS,qAC:[IO91SX] 35 miles NNW of London",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('['),
+			Position: &Position{Latitude: 51.958333, Longitude: -0.500000},
+		},
+		{
+			Raw:      "N0CALL>APRS,qAC:[IO91]",
+			Src:      MustParseAddress("N0CALL"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  1,
+			Type:     DataType('['),
+			Position: &Position{Latitude: 51.0, Longitude: -2.0},
+		},
+		{
+			Raw:      "WX4GSO-9>APN382,qAR,WD4LSS:!3545.18NL07957.08W#PHG5680/R,W,85NC,NCn Mount Shepherd Piedmont Triad NC",
+			Src:      MustParseAddress("WX4GSO-9"),
+			Dst:      MustParseAddress("APN382"),
+			PathLen:  2,
+			Type:     DataType('!'),
+			Position: &Position{Latitude: 35.753000, Longitude: -79.951333},
+		},
+		{
+			Raw:      "PA4TW>APRS,qAS,PA4TW-2:=5216.28N/00510.05Er Remco, DMR:2041014, Soms QRV op PI2NOS",
+			Src:      MustParseAddress("PA4TW"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  2,
+			Type:     DataType('='),
+			Position: &Position{Latitude: 52.271333, Longitude: 5.167500},
+		},
+		{
+			Raw:      "PA4TW-10>APRS,TCPIP*,qAC,FOURTH:=5220.18N/00453.25EIhttp://aprs.pa4tw.nl:14501/",
+			Src:      MustParseAddress("PA4TW-10"),
+			Dst:      MustParseAddress("APRS"),
+			PathLen:  3,
+			Type:     DataType('='),
+			Position: &Position{Latitude: 52.336333, Longitude: 4.887500},
+		},
+		{
+			Raw:      "N0CALL-1>T3PY1Y,KQ1L-8*,WIDE1,WIDE2-1,qAR:=/5L!!<*e7> sTComment",
+			Src:      MustParseAddress("N0CALL-1"),
+			Dst:      MustParseAddress("T3PY1Y"),
+			PathLen:  4,
+			Type:     DataType('='),
+			Position: &Position{Latitude: 49.5, Longitude: -72.75},
+		},
+		{
+			Raw:      "N0CALL-1>T3PY1Y,KQ1L-8*,WIDE1,WIDE2-1,qAR:=/5L!!<*e7>7P[",
+			Src:      MustParseAddress("N0CALL-1"),
+			Dst:      MustParseAddress("T3PY1Y"),
+			PathLen:  4,
+			Type:     DataType('='),
+			Position: &Position{Latitude: 49.5, Longitude: -72.75},
+			Velocity: &Velocity{88.0, 36.2},
+		},
+		{
+			Raw:      "N0CALL-1>T3PY1Y,KQ1L-8*,WIDE1,WIDE2-1,qAR:=/5L!!<*e7>{?!",
+			Src:      MustParseAddress("N0CALL-1"),
+			Dst:      MustParseAddress("T3PY1Y"),
+			PathLen:  4,
+			Type:     DataType('='),
+			Position: &Position{Latitude: 49.5, Longitude: -72.75},
+			Range:    20.13,
+		},
+		{
+			Raw:      "N0CALL-1>T3PY1Y,KQ1L-8*,WIDE1,WIDE2-1,qAR:=/5L!!<*e7OS]S",
+			Src:      MustParseAddress("N0CALL-1"),
+			Dst:      MustParseAddress("T3PY1Y"),
+			PathLen:  4,
+			Type:     DataType('='),
+			Position: &Position{Latitude: 49.5, Longitude: -72.75},
+			Altitude: 10004,
+		},
+		{
+			Raw:      "N0CALL-1>T3PY1Y,KQ1L-8*,WIDE1,WIDE2-1,qAR:@092345z/5L!!<*e7>{?!",
+			Src:      MustParseAddress("N0CALL-1"),
+			Dst:      MustParseAddress("T3PY1Y"),
+			PathLen:  4,
+			Type:     '@',
+			Time:     testTime(9, 23, 45, 0),
+			Position: &Position{Latitude: 49.5, Longitude: -72.75},
+			Range:    20.13,
+		},
+		{
+			Raw:     "PE1ROG-8>APLC13,qAS,PE1ROG-2:!/49[<P'PC>8pQLoRa___MOBIL___TEST",
+			Src:     MustParseAddress("PE1ROG-8"),
+			Dst:     MustParseAddress("APLC13"),
+			PathLen: 2,
+			Type:    '!',
+		},
+		{
+			Raw:     "PE1ROG-1>APPM13,TCPIP*,qAC,T2PRT:>Running on Raspberry Pi with RTL dongle",
+			Src:     MustParseAddress("PE1ROG-1"),
+			Dst:     MustParseAddress("APPM13"),
+			PathLen: 3,
+			Type:    '>',
+		},
+		{
+			Raw:     "PD0MZ-4>APE32L,WIDE1-1,qAR,PD0MZ-10:>LoRa APRS Tracker",
+			Src:     MustParseAddress("PD0MZ-4"),
+			Dst:     MustParseAddress("APE32L"),
+			PathLen: 3,
+			Type:    '>',
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.Raw, func(t *testing.T) {
+			p, err := ParsePacket(test.Raw)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !p.Dst.EqualTo(test.Dst) {
+				t.Fatalf("expected dst %s, got %s", test.Dst, p.Dst)
+			}
+			if !p.Src.EqualTo(test.Src) {
+				t.Fatalf("expected src %s, got %s", test.Src, p.Src)
+			}
+			if len(p.Path) != test.PathLen {
+				t.Fatalf("expected path length %d, got %d: %v", test.PathLen, len(p.Path), p.Path)
+			}
+			if p.Payload.Type() != test.Type {
+				t.Fatalf("expected packet type %s [%c], got %s [%c]",
+					test.Type, test.Type,
+					p.Payload.Type(), p.Payload.Type())
+			}
+			if test.Altitude != 0 {
+				if p.Altitude == 0 {
+					t.Fatalf("expected altitude %f, got none", test.Altitude)
+				}
+				if math.Abs(test.Altitude-p.Altitude) > 1.0 {
+					t.Fatalf("expected altitude %f, got %f", test.Altitude, p.Altitude)
+				}
+			}
+			if test.Velocity != nil {
+				if p.Velocity.Course == 0 {
+					t.Fatalf("expected velocity %v, got none", test.Velocity)
+				}
+				if math.Abs(test.Velocity.Course-p.Velocity.Course) > 1.0 {
+					t.Fatalf("expected course %f, got %f", test.Velocity.Course, p.Velocity.Course)
+				}
+				if math.Abs(test.Velocity.Speed-p.Velocity.Speed) > 1.0 {
+					t.Fatalf("expected speed %f, got %f", test.Velocity.Speed, p.Velocity.Speed)
+				}
+			}
+			if test.Range != 0 {
+				if p.Range == 0 {
+					t.Fatalf("expected range %f, got none", test.Range)
+				}
+				if math.Abs(test.Range-p.Range) > 0.1 {
+					t.Fatalf("expected range %f, got %f", test.Range, p.Range)
+				}
+			}
+			if test.Position != nil {
+				if p.Position == nil {
+					t.Fatalf("expected position %s, got none", test.Position)
+				}
+				if d := testDistance(test.Position, p.Position); d > 1.0 {
+					t.Fatalf("expected position %s, got %s with distance %f meter", test.Position, p.Position, d)
+				}
+			}
+			if test.Time != nil {
+				if p.Time == nil {
+					t.Fatalf("expected time %s", test.Time)
+				}
+				if test.Time.Sub(*p.Time) > time.Minute {
+					t.Fatalf("expected time %s, got %s", test.Time, p.Time)
+				}
+			}
+			//t.Logf("%#+v", p)
+		})
+	}
+}
--- a/protocol/aprs/position.go
+++ b/protocol/aprs/position.go
@@ -0,0 +1,313 @@
+package aprs
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"git.maze.io/go/ham/util/maidenhead"
+)
+
+var (
+	// Position ambiguity replacement
+	disambiguation = []int{2, 3, 5, 6, 12, 13, 15, 16}
+
+	miceCodes = map[rune]map[int]string{
+		'0': {0: "0", 1: "0", 2: "S", 3: "0", 4: "E"},
+		'1': {0: "1", 1: "0", 2: "S", 3: "0", 4: "E"},
+		'2': {0: "2", 1: "0", 2: "S", 3: "0", 4: "E"},
+		'3': {0: "3", 1: "0", 2: "S", 3: "0", 4: "E"},
+		'4': {0: "4", 1: "0", 2: "S", 3: "0", 4: "E"},
+		'5': {0: "5", 1: "0", 2: "S", 3: "0", 4: "E"},
+		'6': {0: "6", 1: "0", 2: "S", 3: "0", 4: "E"},
+		'7': {0: "7", 1: "0", 2: "S", 3: "0", 4: "E"},
+		'8': {0: "8", 1: "0", 2: "S", 3: "0", 4: "E"},
+		'9': {0: "9", 1: "0", 2: "S", 3: "0", 4: "E"},
+		'A': {0: "0", 1: "1 (Custom)"},
+		'B': {0: "1", 1: "1 (Custom)"},
+		'C': {0: "2", 1: "1 (Custom)"},
+		'D': {0: "3", 1: "1 (Custom)"},
+		'E': {0: "4", 1: "1 (Custom)"},
+		'F': {0: "5", 1: "1 (Custom)"},
+		'G': {0: "6", 1: "1 (Custom)"},
+		'H': {0: "7", 1: "1 (Custom)"},
+		'I': {0: "8", 1: "1 (Custom)"},
+		'J': {0: "9", 1: "1 (Custom)"},
+		'K': {0: " ", 1: "1 (Custom)"},
+		'L': {0: " ", 1: "0", 2: "S", 3: "0", 4: "E"},
+		'P': {0: "0", 1: "1 (Std)", 2: "N", 3: "100", 4: "W"},
+		'Q': {0: "1", 1: "1 (Std)", 2: "N", 3: "100", 4: "W"},
+		'R': {0: "2", 1: "1 (Std)", 2: "N", 3: "100", 4: "W"},
+		'S': {0: "3", 1: "1 (Std)", 2: "N", 3: "100", 4: "W"},
+		'T': {0: "4", 1: "1 (Std)", 2: "N", 3: "100", 4: "W"},
+		'U': {0: "5", 1: "1 (Std)", 2: "N", 3: "100", 4: "W"},
+		'V': {0: "6", 1: "1 (Std)", 2: "N", 3: "100", 4: "W"},
+		'W': {0: "7", 1: "1 (Std)", 2: "N", 3: "100", 4: "W"},
+		'X': {0: "8", 1: "1 (Std)", 2: "N", 3: "100", 4: "W"},
+		'Y': {0: "9", 1: "1 (Std)", 2: "N", 3: "100", 4: "W"},
+		'Z': {0: " ", 1: "1 (Std)", 2: "N", 3: "100", 4: "W"},
+	}
+
+	miceMsgTypes = map[string]string{
+		"000":          "Emergency",
+		"001 (Std)":    "Priority",
+		"001 (Custom)": "Custom-6",
+		"010 (Std)":    "Special",
+		"010 (Custom)": "Custom-5",
+		"011 (Std)":    "Committed",
+		"011 (Custom)": "Custom-4",
+		"100 (Std)":    "Returning",
+		"100 (Custom)": "Custom-3",
+		"101 (Std)":    "In Service",
+		"101 (Custom)": "Custom-2",
+		"110 (Std)":    "En Route",
+		"110 (Custom)": "Custom-1",
+		"111 (Std)":    "Off Duty",
+		"111 (Custom)": "Custom-0",
+	}
+)
+
+const (
+	gridChars = "ABCDEFGHIJKLMNOPQRSTUVWX0123456789"
+
+	messageTypeStd    = "Std"
+	messageTypeCustom = "Custom"
+)
+
+// Position contains GPS coordinates.
+type Position struct {
+	Latitude   float64 `json:"latitude"`  // Degrees
+	Longitude  float64 `json:"longitude"` // Degrees
+	Ambiguity  int     `json:"ambiguity,omitempty"`
+	Symbol     Symbol  `json:"symbol"`
+	Compressed bool    `json:"compressed,omitempty"`
+}
+
+func (pos Position) String() string {
+	if pos.Ambiguity == 0 {
+		return fmt.Sprintf("{%f, %f}", pos.Latitude, pos.Longitude)
+	}
+	return fmt.Sprintf("{%f, %f}, ambiguity=%d", pos.Latitude, pos.Longitude, pos.Ambiguity)
+}
+
+func ParseUncompressedPosition(s string) (Position, string, error) {
+	// APRS PROTOCOL REFERENCE 1.0.1 Chapter 8, page 32 (42 in PDF)
+
+	pos := Position{}
+
+	if len(s) < 18 {
+		return pos, "", ErrInvalidPosition
+	}
+
+	b := []byte(s)
+	for _, p := range disambiguation {
+		if b[p] == ' ' {
+			pos.Ambiguity++
+			b[p] = '0'
+		}
+	}
+	s = string(b)
+
+	var (
+		err                        error
+		latDeg, latMin, latMinFrag uint64
+		lngDeg, lngMin, lngMinFrag uint64
+		latHemi, lngHemi           byte
+		isSouth, isWest            bool
+	)
+
+	if latDeg, err = strconv.ParseUint(s[0:2], 10, 8); err != nil {
+		return pos, "", err
+	}
+	if latMin, err = strconv.ParseUint(s[2:4], 10, 8); err != nil {
+		return pos, "", err
+	}
+	if latMinFrag, err = strconv.ParseUint(s[5:7], 10, 8); err != nil {
+		return pos, "", err
+	}
+	latHemi = s[7]
+	pos.Symbol[0] = s[8]
+	if lngDeg, err = strconv.ParseUint(s[9:12], 10, 8); err != nil {
+		return pos, "", err
+	}
+	if lngMin, err = strconv.ParseUint(s[12:14], 10, 8); err != nil {
+		return pos, "", err
+	}
+	if lngMinFrag, err = strconv.ParseUint(s[15:17], 10, 8); err != nil {
+		return pos, "", err
+	}
+	lngHemi = s[17]
+	pos.Symbol[1] = s[18]
+
+	if latHemi == 'S' || latHemi == 's' {
+		isSouth = true
+	} else if latHemi != 'N' && latHemi != 'n' {
+		return pos, "", ErrInvalidPosition
+	}
+
+	if lngHemi == 'W' || lngHemi == 'w' {
+		isWest = true
+	} else if lngHemi != 'E' && lngHemi != 'e' {
+		return pos, "", ErrInvalidPosition
+	}
+
+	if latDeg > 89 || lngDeg > 179 {
+		return pos, "", ErrInvalidPosition
+	}
+
+	pos.Latitude = float64(latDeg) + float64(latMin)/60.0 + float64(latMinFrag)/6000.0
+	pos.Longitude = float64(lngDeg) + float64(lngMin)/60.0 + float64(lngMinFrag)/6000.0
+
+	if isSouth {
+		pos.Latitude = 0.0 - pos.Latitude
+	}
+	if isWest {
+		pos.Longitude = 0.0 - pos.Longitude
+	}
+
+	if pos.Symbol[1] >= 'a' || pos.Symbol[1] <= 'k' {
+		pos.Symbol[1] -= 32
+	}
+
+	if len(s) > 19 {
+		return pos, s[19:], nil
+	}
+	return pos, "", nil
+}
+
+func ParseCompressedPosition(s string) (Position, string, error) {
+	// APRS PROTOCOL REFERENCE 1.0.1 Chapter 9, page 36 (46 in PDF)
+
+	pos := Position{}
+
+	if len(s) < 10 {
+		return pos, "", ErrInvalidPosition
+	}
+
+	// Base-91 check
+	for _, c := range s[1:9] {
+		if c < 0x21 || c > 0x7b {
+			return pos, "", ErrInvalidPosition
+		}
+	}
+
+	var err error
+	var lat, lng int
+	if lat, err = base91Decode(s[1:5]); err != nil {
+		return pos, "", err
+	}
+	if lng, err = base91Decode(s[5:9]); err != nil {
+		return pos, "", err
+	}
+
+	pos.Latitude = 90.0 - float64(lat)/380926.0
+	pos.Longitude = -180.0 + float64(lng)/190463.0
+	pos.Compressed = true
+
+	return pos, s[10:], nil
+}
+
+func ParseMicE(s, dest string) (Position, error) {
+	// APRS PROTOCOL REFERENCE 1.0.1 Chapter 10, page 42 in PDF
+
+	pos := Position{}
+
+	if len(s) < 9 || len(dest) != 6 {
+		return pos, ErrInvalidPosition
+	}
+
+	ns := miceCodes[rune(dest[3])][2]
+	we := miceCodes[rune(dest[5])][4]
+
+	latF := fmt.Sprintf("%s%s", miceCodes[rune(dest[0])][0], miceCodes[rune(dest[1])][0])
+	latF = strings.Trim(latF, ". ")
+	latD, err := strconv.ParseFloat(latF, 64)
+	if err != nil {
+		return pos, ErrInvalidPosition
+	}
+	lonF := fmt.Sprintf("%s%s.%s%s", miceCodes[rune(dest[2])][0], miceCodes[rune(dest[3])][0], miceCodes[rune(dest[4])][0], miceCodes[rune(dest[5])][0])
+	lonF = strings.Trim(lonF, ". ")
+	latM, err := strconv.ParseFloat(lonF, 64)
+	if err != nil {
+		return pos, ErrInvalidPosition
+	}
+	if latM != 0 {
+		latD += latM / 60
+	}
+	if strings.ToUpper(ns) == "S" {
+		latD = -latD
+	}
+
+	lonOff := miceCodes[rune(dest[4])][3]
+	lonD := float64(s[1]) - 28
+	if lonOff == "100" {
+		lonD += 100
+	}
+	if lonD >= 180 && lonD < 190 {
+		lonD -= 80
+	}
+	if lonD >= 190 && lonD < 200 {
+		lonD -= 190
+	}
+
+	lonM := float64(s[2]) - 28
+	if lonM >= 60 {
+		lonM -= 60
+	}
+	// adding hundreth of minute then add minute as deg fraction
+	lonH := float64(s[3]) - 28
+	if lonH != 0 {
+		lonM += lonH / 100
+	}
+	if lonM != 0 {
+		lonD += lonM / 60
+	}
+	if strings.ToUpper(we) == "W" {
+		lonD = -lonD
+	}
+
+	pos.Latitude = latD
+	pos.Longitude = lonD
+
+	return pos, nil
+}
+
+func ParsePositionGrid(s string) (Position, string, error) {
+	var o int
+	for o = 0; o < len(s); o++ {
+		if strings.IndexByte(gridChars, s[o]) < 0 {
+			break
+		}
+	}
+
+	pos := Position{}
+	if o == 2 || o == 4 || o == 6 || o == 8 {
+		p, err := maidenhead.ParseLocator(s[:o])
+		if err != nil {
+			return pos, "", err
+		}
+		pos.Latitude = p.Latitude
+		pos.Longitude = p.Longitude
+	}
+
+	var txt string
+	if o < len(s) {
+		txt = s[o+1:]
+	}
+	return pos, txt, nil
+}
+
+func ParsePosition(s string, compressed bool) (Position, string, error) {
+	if compressed {
+		return ParseCompressedPosition(s)
+	}
+	return ParseUncompressedPosition(s)
+}
+
+func ParsePositionBoth(s string) (Position, string, error) {
+	pos, txt, err := ParseUncompressedPosition(s)
+	if err != nil {
+		return ParseCompressedPosition(s)
+	}
+	return pos, txt, err
+}
--- a/protocol/aprs/symbol.go
+++ b/protocol/aprs/symbol.go
@@ -0,0 +1,266 @@
+package aprs
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+var emptySymbol Symbol
+
+type Symbol [2]byte
+
+func (s Symbol) IsPrimaryTable() bool { return s[0] != '\\' }
+
+func (s Symbol) MarshalJSON() ([]byte, error) {
+	if s == emptySymbol {
+		return json.Marshal("")
+	}
+	return json.Marshal(string(s[:]))
+}
+
+func (s Symbol) get(idx int) (string, error) {
+	var m map[byte]map[int]string
+	if s.IsPrimaryTable() {
+		m = primarySymbol
+	} else {
+		m = alternateSymbol
+	}
+	n, ok := m[s[1]]
+	if !ok {
+		return "", fmt.Errorf("unknown symbol %x", s[1])
+	}
+	if i, ok := n[idx]; ok {
+		return i, nil
+	}
+	return "", fmt.Errorf("symbol doesn't have requested index: %v", n)
+}
+
+func (s Symbol) String() string {
+	hr, err := s.get(1)
+	if err != nil {
+		return err.Error()
+	}
+	return hr
+}
+
+func (s Symbol) SSID() (string, error) {
+	return s.get(2)
+}
+
+func (s Symbol) Emoji() (string, error) {
+	return s.get(3)
+}
+
+func IsValidCompressedSymTable(c byte) bool {
+	return c == '/' ||
+		c == '\\' ||
+		(c >= 0x41 && c <= 0x5a) ||
+		(c >= 0x61 && c <= 0x6a)
+}
+
+func IsValidUncompressedSymTable(c byte) bool {
+	return c == '/' ||
+		c == '\\' ||
+		(c >= 0x41 && c <= 0x5a) ||
+		(c >= 0x30 && c <= 0x39)
+}
+
+var (
+	// Source: http://www.aprs.org/symbols/symbolsX.txt
+	// 0: XYZ code
+	// 1: Human readable
+	// 2: SSID
+	// 3: Emoji
+	primarySymbol = map[byte]map[int]string{
+		'!':  {0: "BB", 1: "Police, Sheriff", 3: ":cop:"},
+		'"':  {0: "BC", 1: "reserved"},
+		'#':  {0: "BD", 1: "Digi"},
+		'$':  {0: "BE", 1: "Phone", 3: ":phone:"},
+		'%':  {0: "BF", 1: "DX Cluster"},
+		'&':  {0: "BG", 1: "HF Gateway"},
+		'\'': {0: "BH", 1: "Small Aircraft", 2: "11", 3: ":airplane:"},
+		'(':  {0: "BI", 1: "Mobile Satellite Station", 3: ":satellite:"},
+		')':  {0: "BJ", 1: "Wheelchair", 3: ":wheelchair:"},
+		'*':  {0: "BK", 1: "Snowmobile"},
+		'+':  {0: "BL", 1: "Red Cross"},
+		',':  {0: "BM", 1: "Boy Scout"},
+		'-':  {0: "BN", 1: "House QTH (VHF)"},
+		'.':  {0: "BO", 1: "X"},
+		'/':  {0: "BP", 1: "Red Dot"},
+		'0':  {0: "P0", 1: "Circle (0)"},
+		'1':  {0: "P1", 1: "Circle (1)"},
+		'2':  {0: "P2", 1: "Circle (2)"},
+		'3':  {0: "P3", 1: "Circle (3)"},
+		'4':  {0: "P4", 1: "Circle (4)"},
+		'5':  {0: "P5", 1: "Circle (5)"},
+		'6':  {0: "P6", 1: "Circle (6)"},
+		'7':  {0: "P7", 1: "Circle (7)"},
+		'8':  {0: "P8", 1: "Circle (8)"},
+		'9':  {0: "P9", 1: "Circle (9)"},
+		':':  {0: "MR", 1: "Fire", 3: ":fire:"},
+		';':  {0: "MS", 1: "Campground", 3: ":tent:"},
+		'<':  {0: "MT", 1: "Motorcycle", 2: "10", 3: ":bike:"},
+		'=':  {0: "MU", 1: "Railroad Engine", 3: ":train:"},
+		'>':  {0: "MV", 1: "Car", 2: "9", 3: ":car:"},
+		'?':  {0: "MW", 1: "File Server"},
+		'@':  {0: "MX", 1: "HC Future"},
+		'A':  {0: "PA", 1: "Aid Station", 3: ":hospital:"},
+		'B':  {0: "PB", 1: "BBS or PBBS"},
+		'C':  {0: "PC", 1: "Canoe"},
+		'D':  {0: "PD"},
+		'E':  {0: "PE", 1: "Eyeball"},
+		'F':  {0: "PF", 1: "Tractor", 3: ":tractor:"},
+		'G':  {0: "PG", 1: "Grid Square"},
+		'H':  {0: "PH", 1: "Hotel", 3: ":hotel:"},
+		'I':  {0: "PI", 1: "TCP/IP"},
+		'J':  {0: "PJ"},
+		'K':  {0: "PK", 1: "School", 3: ":school:"},
+		'L':  {0: "PL", 1: "PC User", 3: ":computer:"},
+		'M':  {0: "PM", 1: "MacAPRS", 3: ":computer:"},
+		'N':  {0: "PN", 1: "NTS Station"},
+		'O':  {0: "PO", 1: "Balloon", 2: "11", 3: ":airplane:"},
+		'P':  {0: "PP", 1: "Police", 3: ":police_car:"},
+		'Q':  {0: "PQ"},
+		'R':  {0: "PR", 1: "Recreational Vehicle", 2: "13", 3: ":car:"},
+		'S':  {0: "PS", 1: "Shuttle"},
+		'T':  {0: "PT", 1: "SSTV"},
+		'U':  {0: "PU", 1: "Bus", 2: "2", 3: ":bus:"},
+		'V':  {0: "PV", 1: "ATV"},
+		'W':  {0: "PW", 1: "National WX Service Site"},
+		'X':  {0: "PX", 1: "Helo", 2: "6"},
+		'Y':  {0: "PY", 1: "Yacht", 2: "5", 3: ":sailboat:"},
+		'Z':  {0: "PZ", 1: "WinAPRS", 3: ":computer:"},
+		'[':  {0: "HS", 1: "Human/Person", 2: "7", 3: ":running:"},
+		'\\': {0: "HT", 1: "DF Station"},
+		']':  {0: "HU", 1: "Post Office", 3: ":post_office:"},
+		'^':  {0: "HV", 1: "Large Aircraft", 3: ":airplane:"},
+		'_':  {0: "HW", 1: "Weather Station", 3: ":cloud:"},
+		'`':  {0: "HX", 1: "Dish Antenna", 3: ":satellite:"},
+		'a':  {0: "LA", 1: "Ambulance", 2: "1", 3: ":ambulance:"},
+		'b':  {0: "LB", 1: "Bike", 2: "4", 3: ":bike:"},
+		'c':  {0: "LC", 1: "Incident Command Post"},
+		'd':  {0: "LD", 1: "Fire Dept", 3: ":fire_engine:"},
+		'e':  {0: "LE", 1: "Horse", 3: ":racehorse:"},
+		'f':  {0: "LF", 1: "Fire Truck", 2: "3", 3: ":fire_engine:"},
+		'g':  {0: "LG", 1: "Glider", 3: ":airplane:"},
+		'h':  {0: "LH", 1: "Hospital", 3: ":hospital:"},
+		'i':  {0: "LI", 1: "IOTA"},
+		'j':  {0: "LJ", 1: "Jeep", 2: "12", 3: ":car:"},
+		'k':  {0: "LK", 1: "Truck", 2: "14", 3: ":truck:"},
+		'l':  {0: "LL", 1: "Laptop", 3: ":computer:"},
+		'm':  {0: "LM", 1: "Mic-E Repeater"},
+		'n':  {0: "LN", 1: "Node"},
+		'o':  {0: "LO", 1: "EOC"},
+		'p':  {0: "LP", 1: "Dog", 3: ":dog2:"},
+		'q':  {0: "LQ", 1: "Grid SQ"},
+		'r':  {0: "LR", 1: "Repeater"},
+		's':  {0: "LS", 1: "Ship", 2: "8", 3: ":ship:"},
+		't':  {0: "LT", 1: "Truck Stop"},
+		'u':  {0: "LU", 1: "Truck (18 Wheeler)", 3: ":truck:"},
+		'v':  {0: "LV", 1: "Van", 2: "15", 3: ":minibus:"},
+		'w':  {0: "LW", 1: "Water Station"},
+		'x':  {0: "LX", 1: "xAPRS", 3: ":computer:"},
+		'y':  {0: "LY", 1: "Yagi @ QTH"},
+		'z':  {0: "LZ"},
+		'{':  {0: "J1"},
+		'|':  {0: "J2", 1: "TNC Stream Switch"},
+		'}':  {0: "J3"},
+		'~':  {0: "J4", 1: "TNC Stream Switch"},
+	}
+	alternateSymbol = map[byte]map[int]string{
+		'!':  {0: "OBO", 1: "Emergency"},
+		'"':  {0: "OC", 1: "Reserved"},
+		'#':  {0: "OD#", 1: "Overlay Digi"},
+		'$':  {0: "OEO", 1: "Bank/ATM", 3: ":atm:"},
+		'%':  {0: "OFO", 1: "Power Plant", 3: ":factory:"},
+		'&':  {0: "OG#", 1: "I=Igte R=RX T=1hopTX 2=2hopTX"},
+		'\'': {0: "OHO", 1: "Crash Site"},
+		'(':  {0: "OIO", 1: "Cloudy", 3: ":cloud:"},
+		')':  {0: "OJO", 1: "Firenet MEO"},
+		'*':  {0: "OK"},
+		'+':  {0: "OL", 1: "Church", 3: ":church:"},
+		',':  {0: "OM", 1: "Girl Scouts", 3: ":tent:"},
+		'-':  {0: "ONO", 1: "House", 3: ":house:"},
+		'.':  {0: "OO", 1: "Ambiguous"},
+		'/':  {0: "OP", 1: "Waypoint Destination"},
+		'0':  {0: "A0#", 1: "Circle", 3: ":red_circle:"},
+		'1':  {0: "A1"},
+		'2':  {0: "A2"},
+		'3':  {0: "A3"},
+		'4':  {0: "A4"},
+		'5':  {0: "A5"},
+		'6':  {0: "A6"},
+		'7':  {0: "A7"},
+		'8':  {0: "A8O", 1: "WiFi Network"},
+		'9':  {0: "A9", 1: "Gas Station", 3: ":fuelpump:"},
+		':':  {0: "NR"},
+		';':  {0: "NSO", 1: "Park/Picnic"},
+		'<':  {0: "NTO", 1: "Advisory"},
+		'=':  {0: "NUO"},
+		'>':  {0: "NV#", 1: "Cars & Vehicles", 3: ":car:"},
+		'?':  {0: "NW", 1: "Info Kiosk"},
+		'@':  {0: "NX", 1: "Hurricane", 3: ":cyclone:"},
+		'A':  {0: "AA#", 1: "Box DTMF & RFID"},
+		'B':  {0: "AB"},
+		'C':  {0: "AC", 1: "Coast Guard"},
+		'D':  {0: "ADO", 1: "Depots"},
+		'E':  {0: "AE", 1: "Smoke"},
+		'F':  {0: "AF"},
+		'G':  {0: "AG"},
+		'H':  {0: "AHO", 1: "Haze"},
+		'I':  {0: "AI", 1: "Rain Shower", 3: ":umbrella:"},
+		'J':  {0: "AJ"},
+		'K':  {0: "AK", 1: "Kenwood HT"},
+		'L':  {0: "AL", 1: "Lighthouse"},
+		'M':  {0: "AMO", 1: "MARS"},
+		'N':  {0: "AN", 1: "Navigation Buoy"},
+		'O':  {0: "AO", 1: "Rocket", 3: ":rocket:"},
+		'P':  {0: "AP", 1: "Parking", 3: ":parking:"},
+		'Q':  {0: "AQ", 1: "Quake"},
+		'R':  {0: "ARO", 1: "Restaurant"},
+		'S':  {0: "AS", 1: "Satellite/Pacsat", 3: ":rocket:"},
+		'T':  {0: "AT", 1: "Thunderstorm"},
+		'U':  {0: "AU", 1: "Sunny"},
+		'V':  {0: "AV", 1: "VORTAC Nav Aid"},
+		'W':  {0: "AW#", 1: "NWS Site"},
+		'X':  {0: "AX", 1: "Pharmacy"},
+		'Y':  {0: "AYO", 1: "Radios and devices"},
+		'Z':  {0: "AZ"},
+		'[':  {0: "DSO", 1: "W. Cloud"},
+		'\\': {0: "DTO", 1: "GPS"},
+		']':  {0: "DU"},
+		'^':  {0: "DV#", 1: "Other Aircraft", 3: ":airplane:"},
+		'_':  {0: "DW#", 1: "WX Site"},
+		'`':  {0: "DX", 1: "Rain", 3: ":umbrella:"},
+		'a':  {0: "SA#O"},
+		'b':  {0: "SB"},
+		'c':  {0: "SC#O", 1: "CD Triangle"},
+		'd':  {0: "SD", 1: "DX Spot"},
+		'e':  {0: "SE", 1: "Sleet"},
+		'f':  {0: "SF", 1: "Funnel Cloud"},
+		'g':  {0: "SG", 1: "Gale Flags"},
+		'h':  {0: "SHO", 1: "Store or Hamfest"},
+		'i':  {0: "SI#", 1: "Box / POI"},
+		'j':  {0: "SJ", 1: "Work Zone"},
+		'k':  {0: "SKO", 1: "Special Vehicle"},
+		'l':  {0: "SL", 1: "Areas"},
+		'm':  {0: "SM", 1: "Value Sign"},
+		'n':  {0: "SN#", 1: "Triangle"},
+		'o':  {0: "SO", 1: "Small Circle"},
+		'p':  {0: "SP"},
+		'q':  {0: "SQ"},
+		'r':  {0: "SR", 1: "Restrooms"},
+		's':  {0: "SS#", 1: "Ship/Boats", 3: ":speedboat:"},
+		't':  {0: "ST", 1: "Tornado", 3: ":cyclone:"},
+		'u':  {0: "SU#", 1: "Truck", 3: ":truck:"},
+		'v':  {0: "SV#", 1: "Van", 3: ":minibus:"},
+		'w':  {0: "SWO", 1: "Flooding"},
+		'x':  {0: "SX", 1: "Wreck/Obstruction"},
+		'y':  {0: "SY", 1: "Skywarn"},
+		'z':  {0: "SZ#", 1: "Shelter"},
+		'{':  {0: "Q1"},
+		'|':  {0: "Q2", 1: "TNC Stream Switch"},
+		'}':  {0: "Q3"},
+		'~':  {0: "Q4", 1: "TNC Stream Switch"},
+	}
+)
--- a/protocol/aprs/time.go
+++ b/protocol/aprs/time.go
@@ -0,0 +1,33 @@
+package aprs
+
+import (
+	"fmt"
+	"time"
+)
+
+type TimeFormatError struct {
+	Time string
+}
+
+func (err TimeFormatError) Error() string {
+	return fmt.Sprintf("aprs: unknown time stamp %q", err.Time)
+}
+
+func ParseTime(s string) (time.Time, error) {
+	if len(s) < 7 {
+		return time.Time{}, TimeFormatError{s}
+	}
+
+	switch {
+	case s[6] == 'z': // Day/Hours/Minutes (DHM) format
+		return time.Parse("021504", s[:6])
+	case s[6] == '/': // Day/Hours/Minutes (DHM) format
+		return time.Parse("021504", s[:6])
+	case s[6] == 'h': // Hours/Minutes/Seconds (HMS) format
+		return time.Parse("150405", s[:6])
+	case len(s) >= 8: // Month/Day/Hours/Minutes (MDHM) format
+		return time.Parse("01021504", s[:8])
+	default:
+		return time.Time{}, TimeFormatError{s}
+	}
+}