| --- |
| license: cc-by-4.0 |
| task_categories: |
| - audio-classification |
| - object-detection |
| tags: |
| - drone-detection |
| - counter-uas |
| - acoustic-array |
| - cue-to-track |
| - ablation |
| pretty_name: "nightjar flight 2026-08-06 #2 — chirp guard off: the cue chain closes" |
| --- |
| |
| # nightjar flight 2026-08-06, session 2 — the fix, and a producer swap mid-session |
|
|
| The "after" half of a same-evening, same-site A/B against `nightjar-flight-20260806-1`, where the |
| chirp guard vetoed the drone outright. Here the guard is disabled and the gate **cues while the |
| drone is airborne** (0 → 8). ⚠ **But GPS scoring (added after first publication) shows the |
| optical "locks" were NOT the drone and most cheap-gate cues were a second site emitter** — see |
| the scored findings below. An earlier revision of this card claimed "the full chain fires"; |
| that claim is RETRACTED. |
|
|
| ⚠ **This session contains TWO different cue producers.** Treat it as two segments, not one: |
|
|
| | segment | UTC | producer | chirp guard | |
| |---|---|---|---| |
| | A | 00:25:15 – 00:42:28 | `cue_daemon_subhunt.py` (ft16 neural) | **off** | |
| | B | 00:42:28 – 00:53:27 | `cue_daemon.py` (cheap gate) | **off** | |
|
|
| The swap was made live because SubHunt was starving the cue rate (below). |
|
|
| ## ★ Finding 1 — the chirp guard was real, but it was not the only problem |
|
|
| With `CHIRP_GUARD=0` the gate produces **8 cues coincident with an airborne drone** (session 1: |
| zero). That part of the fix stands. |
|
|
| ⚠ **Scored against the DJI GPS record, most of those cues are NOT the drone either:** |
|
|
| | cue disposition (14 total) | n | |
| |---|---| |
| | fired while the drone was **not airborne** | 6 | |
| | pinned at array az **322.6–323.4** — a **second fixed site emitter** | 6 | |
| | consistent with the drone | **2** (SubHunt az 184.0 vs GPS 193.0 = **−9.0°**; one cheap az 164.4 vs 208.9 = −44.5°, marginal) | |
|
|
| Best-fit constant-offset residual over the 8 airborne-coincident cues: **56.5° robust sigma, |
| 12% within 10°** — the beamformer mostly locked the loudest static source, not the drone. |
|
|
| ⚠ Lesson recorded: **wandering `line_hz` is NOT a drone signature by itself.** The az-323 |
| emitter cluster wanders 363–1166 Hz (the peak-picker hops harmonics on a stationary machine) |
| while its **bearing stays pinned to 0.8°**. Bearing spread is the discriminator; frequency |
| spread fooled the first read of this data. |
| |
| ## ★ Finding 2 — SubHunt starves the agreement window on this hardware |
| |
| | | segment A (SubHunt) | segment B (cheap) | |
| |---|---|---| |
| | duration | 17.2 min | 11.0 min | |
| | cue candidates | **1** | **13** | |
| |
| The gate needs **4 agreeing bearings inside a 5 s window at ~1 Hz**. SubHunt logged |
| `analysis behind, skipped ~81 hops` over ~825 hops (~10 %). That rate is the documented |
| steady-state, **not** the retracted "runaway" — but losing one hop in ten still prevents the |
| 4-of-5 s window from filling. **The 2026-08-05 preallocated-ring fix is real and present** |
| (1 startup overrun, skips flat); it removed the ALSA overruns but did not make ft16 fast |
| enough to sustain the gate under a live tracker. |
| |
| ⚠ **Rate is not accuracy.** GPS scoring reverses the quality read: SubHunt's single cue was |
| the **only clearly drone-consistent bearing of the session** (−9.0° vs truth), while the cheap |
| gate's 13 cues were dominated by the az-323 emitter and not-airborne false alarms. n=1 proves |
| nothing about ft16 either — but do not cite this session as "cheap gate beats SubHunt"; on |
| bearing truth it was the other way around. |
| |
| ## Tracker outcome |
| |
| | | session 1 (guard ON) | **session 2 (guard OFF)** | |
| |---|---|---| |
| | track active | 0.2 % | **5.7 %** | |
| | frames with detection | 1 | **83** | |
| | track episodes | 1 (2.0 s) | **22** (longest 7.6 s) | |
| | max focal | 15.17 mm | 11.59 mm (2.70x) | |
| | SEARCH | 96.6 % | 89.7 % | |
| |
| ⚠ **The FSM numbers above are NOT drone locks.** Scored against GPS (256 tracked samples with |
| truth within 2 s): camera-implied bearing vs drone bearing has **27.5° robust sigma after |
| removing the best-fit constant offset — a time-shuffled placebo scores 27.2°**, i.e. the real |
| pairing beats exactly 50 % of random pairings. The 22 episodes were clutter (treeline / cloud |
| edges), indistinguishable from real locks in the FSM but not pointed anywhere near the drone. |
| An earlier revision of this card counted them as drone acquisitions; that is RETRACTED. |
| |
| The honest statement: the guard fix restored *cueing*; nothing in this session demonstrates a |
| verified optical lock on the drone. (Caveat on the scoring itself: rig position was taken from |
| the 07-27 survey and the rig moved 08-05 — at 24–83 m slant a ~10 m rig-position error is up |
| to ~13° of bearing, which inflates the residuals but cannot produce a placebo-level track |
| result or the pinned az-323 cue cluster.) |
| |
| ⚠ **`cue.blob_seed: true` was enabled for the first time on 2026-08-06 and is present in both |
| sessions. It is NOT yet validated** — no analysis here separates blob-seeded acquisitions from |
| YOLO-seeded ones. Do not credit it for the improvement above; the controlled variable between |
| the two sessions is the chirp guard, not blob seeding. |
|
|
| ## Drone truth — two flights |
|
|
| `dji/` holds both records. **Flight A spans the session boundary**; flight B is wholly inside. |
|
|
| | | flight A `[20-15-21]` | flight B `[20-37-43]` | |
| |---|---|---| |
| | airborne | 00:15:21 – 00:28:10 UTC | 00:37:43 – 00:50:47 UTC | |
| | captured here | 00:25:15 – 00:28:10 (**175 s**) | **784 s** (all) | |
| | also in | session 1 (287 s) | — | |
| | max slant | 84 m | **138 m** | |
| | max height | 51 m | 47 m | |
| | elevation | median 17, p90 31 deg | median 26, p90 44 deg | |
| | bearing from rig | 172 – 264 deg | 166 – 302 deg | |
|
|
| Operator notes the drone flew approximately the same positions in both sorties, which is what |
| makes the session-1 / session-2 comparison fair. |
|
|
| ⚠ **DJI stamp sparsity: 5 of 7,846 rows (flight B) and 7 of 7,694 (flight A) carry a valid |
| `CUSTOM.dateTime`.** Anchor ONCE off the first valid stamp and derive every row from |
| `OSD.flyTime`. |
|
|
| ⚠ **Timezone:** Jetson clock is Denver (MDT); DJI wall-stamps are US Eastern. Filename |
| `[20-37-43]` is 00:37:43 UTC the next day. |
|
|
| ## Configuration in force |
|
|
| ``` |
| cue producer SubHunt (ft16) then cheap gate - SEE SEGMENT TABLE ABOVE |
| chirp guard OFF (CHIRP_GUARD=0; no KT pinger was running) |
| detector.mode day |
| yolo_engine nightjar_v3.pt (yolo_conf 0.15 / seed 0.45 / imgsz 1280) |
| cue.blob_seed true (unvalidated) |
| search.scan_enabled false - SEARCH holds for a cue, it does not sweep |
| UMA-16 az_offset_deg 297.644 invert_az true |
| SB-POLARIS NOT RECORDED |
| ``` |
|
|
| ⚠ **SB-POLARIS produced no audio**: the card dropped off the USB bus before session 1 and did not |
| return. **UMA-16 only** for both sessions of 2026-08-06. |
|
|
| ## Contents |
|
|
| ``` |
| audio/uma16_<epoch>.wav UMA-16, 16 ch, 48 kHz, S16_LE, 5-min splits |
| audio/cue_log.jsonl every candidate and reject, both producers |
| video_segments.tar 1080p native + 768x432 substream, H.264, 60 s MPEG-TS |
| blackbox/state.jsonl tracker FSM ~3 Hz: state, pose, focal, detection, track |
| blackbox/frames.tar 1,760 substream stills |
| dji/ both DJI FlightRecords (txt + decoded csv + geojson) |
| ``` |
|
|
| **Channel identity is not guessable.** UMA-16 0-based channel 9 is dead — exclude it, run on 15. |
| Load the serpentine geometry from `uma16_geom.json`. |
|
|
| ## Open questions this session raises |
|
|
| 1. **Tune the chirp guard rather than disabling it.** Reject records now log `hi` and `hi_med`, so |
| an absolute floor (or the cheap gate presence-override) can be fitted instead of `CHIRP_FACTOR` |
| alone. Porting `chirp_ovr` into the SubHunt daemon is the obvious fix. |
| 2. **The az-323 emitter needs suppression** (survey it; a bearing mask now exists in the cheap |
| daemon: `AZ_MASK="315-331"`, logging `ev:az_masked`). |
| 3. **A verified drone lock is still outstanding** — next session runs a truth-scored look-away |
| drill (hovering drone at a surveyed station) instead of free flight, so every cue and every |
| lock is scored against a fixed truth pose at the moment it happens. |
| 4. **Fresh rig GPS fix needed** — all bearing scoring above leans on the 07-27 rig position. |
|
|
| ## Companion |
|
|
| * `nightjar-flight-20260806-1` — same evening, guard ON, the negative control. |
|
|
| ## Elevation datum (fit_el_datum, 2026-08-16) |
|
|
| **Status: FEW_ON_DRONE** — this day's elevation datum is honestly UNSOLVABLE from |
| banked data (camera never/rarely locked on the drone). |
| Close-range elevation truth for this day remains datum-limited (~25 deg |
| floor). Tool: `sirch613/subhunt-v2` `v3/fit_el_datum.py`; summary: |
| `joshruby/acoustic-knowledge` -> `v3/assets/el_datum/SUMMARY.json`. |
|
|
