Skip to content

Update Label 21 POSN — decode track/GS/wind #420

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
thepacket wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Update Label 21 POSN — decode track/GS/wind #420

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
130 changes: 104 additions & 26 deletions lib/plugins/Label_21_POS.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,42 @@ import { DecoderPlugin } from '../DecoderPlugin';
import { DecodeResult, Message, Options } from '../DecoderPluginInterface';
import { ResultFormatter } from '../utils/result_formatter';

// Position Report
/**
* Label 21 — Periodic Position Report (POSN)
*
* Automatic in-flight position report transmitted by the FMS/ACARS unit at
* regular intervals. Carries location, ground track, time, altitude, speed,
* wind, OAT, ETA, and destination.
*
* Wire format (after the `POS` preamble — note that the trailing `N` of
* `POSN` becomes the first character of the body):
*
* N 34.398W 80.393, 85,230818,35019,24306, 92,-54,235606,KBWI
* | | | | | | | | | | |
* | | | | | | | | | | └ Destination ICAO
* | | | | | | | | | └─────── ETA, HHMMSS UTC
* | | | | | | | | └─────────── OAT (°C, may be negative)
* | | | | | | | └─────────────── Wind speed (kt)
* | | | | | | └─────────────────────── Groundspeed × 100
* | | | | | | (raw integer; 24306 → 243.06 kt)
* | | | | | └───────────────────────────── Altitude (ft MSL)
* | | | | └──────────────────────────────────── Time of position, HHMMSS UTC
* | | | └─────────────────────────────────────── Ground track (degrees true)
* | | └─────────────────────────────────────────────── Longitude (deg, sign from hemisphere)
* | └─────────────────────────────────────────────────────── Longitude hemisphere (E/W)
* └───────────────────────────────────────────────────────── Latitude (deg) — leading hemisphere
* char (N/S) supplied by the trailing
* `N` of `POSN`; observed examples are
* all northern.
*
* Variants seen in the wild (longitude width 6 or 7 chars, optional space):
* N 34.398W 80.393, ... (lon < 100)
* N 37.761W121.680, ... (lon ≥ 100, no space)
*
* Per the analyst's "wild-guess → ignore" guidance, latitude is parsed as
* implicitly North when the hemisphere letter is the trailing `N` of `POSN`;
* a leading `S` would be honoured but is undocumented.
*/
export class Label_21_POS extends DecoderPlugin {
name = 'label-21-pos';

Expand All @@ -22,30 +57,72 @@ export class Label_21_POS extends DecoderPlugin {
const content = message.text.substring(3);
const fields = content.split(',');

if (fields.length == 9) {
// POSN 37.550W 76.436, 98,110800,23961,25820, 65,-23,114212,KRDU
if (fields.length === 9) {
// ── Position (field 0) ──
processPosition(decodeResult, fields[0].trim());

// ── Field 1: ground track (degrees true) ──
const trackRaw = fields[1].trim();
if (/^\d{1,3}$/.test(trackRaw)) {
const track = Number(trackRaw);
decodeResult.raw.track = track;
decodeResult.formatted.items.push({
type: 'track',
code: 'TRK',
label: 'Ground Track',
value: `${track}°`,
});
}

// ── Field 2: time of position, HHMMSS ──
ResultFormatter.timestamp(
decodeResult,
DateTimeUtils.convertHHMMSSToTod(fields[2]),
);

// ── Field 3: altitude (ft MSL) ──
ResultFormatter.altitude(decodeResult, Number(fields[3]));

// ── Field 4: groundspeed × 100 (raw) ──
const gsRaw = fields[4].trim();
if (/^\d{3,6}$/.test(gsRaw)) {
const gsKts = Number(gsRaw) / 100;
decodeResult.raw.ground_speed = gsKts;
decodeResult.formatted.items.push({
type: 'ground_speed',
code: 'GS',
label: 'Ground Speed',
value: `${gsKts.toFixed(2)} kt`,
});
}

// ── Field 5: wind speed (kt) ──
const windRaw = fields[5].trim();
if (/^-?\d{1,3}$/.test(windRaw)) {
const wind = Number(windRaw);
decodeResult.raw.wind_speed = wind;
decodeResult.formatted.items.push({
type: 'wind_speed',
code: 'WIND',
label: 'Wind Speed',
value: `${wind} kt`,
});
}

// ── Field 6: OAT (°C) ──
ResultFormatter.temperature(decodeResult, fields[6].replace(/ /g, ''));

// ── Field 7: ETA, HHMMSS ──
ResultFormatter.eta(
decodeResult,
DateTimeUtils.convertHHMMSSToTod(fields[7]),
);
ResultFormatter.arrivalAirport(decodeResult, fields[8]);

ResultFormatter.unknownArr(decodeResult, [
fields[1],
fields[4],
fields[5],
]);
// ── Field 8: destination ICAO ──
ResultFormatter.arrivalAirport(decodeResult, fields[8]);

this.setDecodeLevel(decodeResult, true, 'partial');
this.setDecodeLevel(decodeResult, true, 'full');
} else {
// Unknown!
this.debug(
options,
`Unknown variation. Field count: ${fields.length}, content: ${content}`,
Expand All @@ -55,23 +132,24 @@ export class Label_21_POS extends DecoderPlugin {
return decodeResult;
}
}

/**
* Parse the position field. Accepts both spaced and unspaced forms:
* "N 34.398W 80.393"
* "N 37.761W121.680"
* "S 33.940E151.180" (hypothetical southern/eastern; not observed)
*/
function processPosition(decodeResult: DecodeResult, value: string) {
// N 39.841W 75.790
if (
value.length !== 16 &&
value[0] !== 'N' &&
value[0] !== 'S' &&
value[8] !== 'W' &&
value[8] !== 'E'
) {
return;
}
const latDir = value[0] === 'N' ? 1 : -1;
const lonDir = value[8] === 'E' ? 1 : -1;
const m = value.match(
/^([NS])\s*(\d+(?:\.\d+)?)\s*([EW])\s*(\d+(?:\.\d+)?)$/,
);
if (!m) return;

const latDir = m[1] === 'N' ? 1 : -1;
const lonDir = m[3] === 'E' ? 1 : -1;
const position = {
latitude: latDir * Number(value.substring(1, 7)),
longitude: lonDir * Number(value.substring(9, 15)),
latitude: latDir * Number(m[2]),
longitude: lonDir * Number(m[4]),
};

ResultFormatter.position(decodeResult, position);
}