Update Label 21 POSN — decode track/GS/wind

[thepacket]

Extends Label_21_POS to decode previously-unknown fields in the 9-field POSN format:

• Field 1 → ground track (degrees)
• Field 4 → ground speed ÷ 100 (kt) — raw 24306 = 243.06 kt
• Field 5 → wind speed (kt)

Fixes position parsing to handle both spaced (N 34.398W 80.393) and unspaced (N 37.761W121.680) forms, and includes the final digit of each coordinate that the previous substring bounds dropped.

Decode level bumped from partial to full.

npm run build passes.

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Reviewing files that changed from the base of the PR and between 10f9f69 and 50a047d.

📒 Files selected for processing (1)

• lib/plugins/Label_21_POS.ts

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[kevinelliott]

Summary

Extends Label_21_POS to decode previously-unknown fields in the 9-field POSN format: ground track (field 1), groundspeed × 100 (field 4), and wind speed (field 5). Also rewrites processPosition to use a single regex that handles both spaced (N 34.398W 80.393) and unspaced (N 37.761W121.680) longitude forms, and captures the trailing decimal digit that the previous fixed-width substring dropped. Decode level bumped partial → full.

Verdict

Comment-only review. The intent is solid: the previous code had buggy hemisphere-letter logic (used && where || was needed, so the guard never triggered) and dropped a digit of precision. The new regex-based parser is cleaner and more correct. Cannot merge as-is — it breaks the existing test.

Must Fix

1. Existing test fails. Label_21_POS.test.ts:28 asserts decodeLevel === 'partial' and items.length === 6. With the new code, decodeLevel is full and items count grows to 8 (added Track, GS, Wind). Also:

   • items[0].value was '39.840 N, 75.790 W' (lossy — note the trailing 0) — with the new regex it should now be '39.841 N, 75.790 W' (correct, full precision).
   • remaining.text === ' 220,22051, 34' becomes '' because unknownArr is no longer called.

   Please update the test. The existing assertion '39.840 N, 75.790 W' is itself a fingerprint of the old precision bug — fixing it to '39.841 N, 75.790 W' should be called out in the diff so reviewers know it's intentional.

2. Per-message coordinate change: the position string changes for any longitude or latitude where the dropped digit was non-zero. This is a small but real output change. Mention it in the PR body so consumers don't get surprised.

Should Fix

• The position regex ^([NS])\s*(\d+(?:\.\d+)?)\s*([EW])\s*(\d+(?:\.\d+)?)$ is permissive — it will accept N99999E99999 etc. Tightening to bounded magnitudes (lat ≤ 90, lon ≤ 180) would prevent garbage decode of malformed messages. The existing code at least had a length guard. Currently the new code only requires the pattern to match — it never validates magnitudes.
• Documentation says "raw integer; 24306 → 243.06 kt" but you toFixed(2) the result. For 25820 / 100 = 258.20 that's fine; for an integer-divisible case like 24300 / 100 = 243.00 the output 243.00 kt is slightly noisy. Consider Number((gsKts).toFixed(2)) or gsKts.toFixed(2).replace(/\.?0+$/, ''). Minor.

Nits

• groundspeed formatter exists in ResultFormatter (line 301 of result_formatter.ts) and emits ${value} knots with code GSPD. You instead inline a custom row with code GS and unit kt. Consider using the formatter for consistency with other plugins (Label 10/12/15 etc.) — though it would round to integer kt rather than two decimals. Worth at least a comment explaining why you diverged.
• Same point for wind: there is no windSpeed formatter today, so a custom row is fine, but be aware the existing windData formatter handles wind-with-direction in route reports.
• Typo "aiports" → "airports" — already fixed in the diff. Good.

Backward Compat / Regression Risk

• Loosening processPosition from 16-char fixed format to a regex broadens what's accepted. The OLD code had a buggy guard (used && instead of ||, so it always returned without effect — meaning all messages reached the substring extraction regardless). So functionally, the parser was already accepting anything; this PR just makes the parser correct. Net: lower regression risk than it looks.
• The &&/|| guard fix means the function used to silently produce NaN for non-N/S leading messages. New code returns cleanly. Strict improvement.
• Output changes: dropped unknownArr of fields 1/4/5 → these now appear as labelled rows. Consumers reading remaining.text for those values will lose them. Reasonable.

Test Coverage

Currently narrower (test breaks). Once updated:

• Add a fixture with longitude ≥ 100° (e.g. N 37.761W121.680 from your PR body) to lock the unspaced variant.
• Add a southern-hemisphere or eastern-hemisphere fixture if you can find one — the docblock says they're hypothetical. If unobserved, fine to skip but a unit test of the regex with synthetic input would be cheap.
• Assert the new Track, GS, Wind rows by code/value.

Outstanding Existing Comments

None. Only an auto-generated CodeRabbit rate-limit notice on the PR.

Thanks @thepacket! Position-parser fix is clearly correct and the new decoded fields are valuable. Please update the test fixture and call out the coordinate-precision change in the description.