Datasets:

joshruby
/

nightjar-flight-20260813

license: cc-by-4.0
task_categories:
  - audio-classification
  - object-detection
tags:
  - drone-detection
  - counter-uas
  - acoustic-array
  - self-calibrating-threshold
  - cue-to-track
pretty_name: >-
  nightjar flight 2026-08-13 — first sortie with a self-calibrated presence
  threshold

nightjar flight 2026-08-13 — self-calibrated presence gate, fast cue chain

First field session where the acoustic presence threshold was measured from the site's own drone-free preroll instead of using the 2026-07-27 constant. Also the first with a fast-reaction cue gate. Both arrays recorded at full native depth.

★ Headline: the presence threshold was ~8 dB too strict, and it is not static

Calibrated live from 151 drone-free ambient blocks (150 s, band 100–1200 Hz):

TRACK  8.87 dB (p99)     was 14.6      ambient median 3.67, max 10.98
SEARCH 6.93 dB (p95)     was 10.0      not clamped

The shipped 14.6 dB constant was this site's p99 on 2026-07-27. Today's site measures 3.67 dB median — the gate was roughly 8 dB above where the noise actually sits, which is why earlier sorties detected on so few windows.

⚠ And the ambient does not hold still. ambient_drift telemetry (a rolling p95, logged once a minute, 20 samples) ranged 7.15 → 15.75 dB, wandering up to 8.82 dB from the frozen 6.93 preroll value. That is far past the ~2 dB that would justify rolling recalibration.

⚠⚠ BUT do not read that as pure ambient drift. The drone was airborne for much of this session, and ambient_drift measures the rolling p95 of the presence statistic whatever the source — a loud drone inflates it directly. This log therefore cannot separate ambient non-stationarity from the drone's own contribution. The honest next step is a drone-free recording of similar length; until then the 8.82 dB figure is an upper bound on drift, not a measurement of it.

Cue chain


candidates	132
posted	50
az-masked (site emitters suppressed)	16
cue az	median 144.9, sd 44.8
presence at cue	median 12.0 dB, min 7.7

Mid-session the gate was retuned live for reaction speed (daemon restarted into the same session; video/blackbox never stopped):

M_AGREE           4 -> 3     agreement window fills a second sooner
CUE_MIN_PERIOD_S 12 -> 4     corrections every 4 s instead of 12
PRESENCE_DB pinned 8.87/6.93 (skips the 150 s preroll on restart)

Measured effect: posts began landing at the 4 s floor (gaps 4.0, 5.0, 4.0 s) versus ~20 s before. The pre-change timeline is in the log: first faint contact at t+359 s, first POST at t+367 (8 s, dominated by the 4-of-5 s agreement gate), second POST at t+381 (the 12 s refractory). Longer gaps afterwards are CUE_SUPPRESS_DEG correctly staying quiet while the camera was already on target — not a failure.

AZ_MASK="281-297,319-335" suppressed the utility-pole transformer (array az 289.2) and emitter-B (327.5). ⚠ The mask is expressed in ARRAY azimuth while the emitters are fixed in the WORLD, so it silently stops working after any registration change — see ~/Desktop/TRANSFORMERS.md.

Tracker (blackbox, 21.6 min, 3,763 samples)

SEARCH 1750 | TRACK 809 | COAST 365 | ACQUIRE 250 | IDLE 571 | REACQUIRE 18
track active 1431 samples (38%), of which 937 YOLO-vouched
pick source while tracking:  blob 520 | yolo 289
focal while tracking: median 9.2 mm, max 83.1 mm (19x)

⚠ No GPS truth was captured for this session (no DJI FlightRecord exported at time of writing), so none of the tracking above is confirmed to be the drone. On 2026-08-12 an identical-looking 38%-tracked session turned out to be on-drone only inside ~25 m and 0% on-drone beyond it. Do not cite these numbers as detection performance without scoring them. The test that settles it is differential — correlate CHANGES in tracker bearing against CHANGES in GPS truth bearing; absolute-error scoring is circular.

Registration in force

UMA-16      az_offset 302.2   invert_az true    (JBL far-anchored, 42 dB SNR)
SB-POLARIS  az_offset 339.55  invert_az FALSE   (2 beacons, handedness margin 2.45 vs 50.85)

audio/uma16_<epoch>.wav   UMA-16, 16 ch, 48 kHz, S32_LE (32-bit, verified from headers)
audio/sb_<epoch>.wav      SB-POLARIS, 8 ch, 48 kHz, S32_LE
audio/cue_log.jsonl       every candidate, mask event, presence_cal and ambient_drift record
audio/uma.log             daemon log incl. the calibration line
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, blob_seeded
blackbox/frames.tar       9,495 substream stills

⚠ Both arrays are S32_LE. Reading them as int16 splits every sample, scrambles channel identity and destroys the spectrum. The UMA16v2 is natively 32-bit; every wav banked before 2026-08-09 was silently truncated to the top 16 bits.

Channel identity is not guessable. UMA-16 0-based channel 9 is a dead electronic-floor channel — exclude it, run on 15. Load the serpentine geometry from uma16_geom.json.

Known-good replay reference

Presence detection replayed over two GPS-truthed flights, channel-agreement gate applied:

threshold	flight A	flight B
14.6 (old constant)	3.8%	16.6%
6.55	67.6%	66.3%
4.71	84.1%	79.9%

These are window-level presence detections. A posted cue must additionally clear bearing consistency, the az mask and the refractory, so cue availability sits at or below these figures.