| --- |
| license: cc-by-4.0 |
| task_categories: |
| - object-detection |
| - audio-classification |
| tags: |
| - drone-detection |
| - counter-uas |
| - acoustic-array |
| - ptz-tracking |
| - multimodal |
| - gps-truth |
| pretty_name: "nightjar field flight 2026-08-04 — cue chain + first live setpoint-zoom exercise" |
| --- |
| |
| # nightjar flight — 2026-08-04 |
|
|
| One 20.9-minute drone sortie recorded end-to-end by the nightjar rig: PTZ camera under |
| closed-loop acoustic-cued optical tracking, two microphone arrays, full autopilot telemetry, |
| and the tracker's own decision log. **GPS truth is exceptionally clean here — 12,447 valid |
| UTC stamps out of 12,448 rows** (a prior session in this series had exactly 1, which made it |
| unusable for anything truth-referenced). |
|
|
| Rig, site and method: see the companion sessions in this series and `SENSIBELSPECS.md` / |
| `SUBHUNTBLACKPAPER.md` in the project. |
|
|
| ## Envelope |
|
|
| | | | |
| |---|---| |
| | airborne | 1252 s (20.9 min), 12,448 GPS fixes at 10 Hz | |
| | max height | 276 m | |
| | max slant range | **473 m** (furthest of the series to date) | |
| | max horizontal speed | 10.5 m/s (24 mph) | |
| | path flown | 3021 m | |
| | window (UTC) | 16:46:25 – 17:07:17 | |
|
|
| ## Contents |
|
|
| ``` |
| audio/uma16_<epoch>.wav UMA-16, 16 ch, 48 kHz, S16_LE, 5-min splits |
| audio/sb_<epoch>.wav SB-POLARIS, 8 ch, 48 kHz, S32_LE, 5-min splits |
| audio/cue_log.jsonl acoustic cue gate: start / cue_candidate / chirp_reject |
| video_segments.tar 1080p native + 768x432 substream, H.264 -c copy, 60 s MPEG-TS |
| blackbox/state.jsonl tracker FSM at ~2.9 Hz: state, pose, focal, error, detection, track |
| blackbox/*_frames.tar 7,135 substream stills |
| dji/*.csv decoded DJI FlightRecord (CUSTOM.dateTime = true UTC) |
| dji/*.txt original encrypted FlightRecord |
| ``` |
|
|
| **Channel identity matters and is not guessable.** UMA-16 0-based channel 9 is a dead |
| electronic-floor channel — exclude it, run on 15. SB-POLARIS has 3 live capsules of 8, and |
| **this session they are `[0, 3, 5]`** (measured: live ~−70 dBFS, dead ~−190 dBFS). The live |
| set has changed between sessions, so detect it by RMS rather than hardcoding. UMA channel |
| order is serpentine — load the geometry file, never hand-derive it. |
|
|
| ⚠ **The two arrays use DIFFERENT sample widths** (UMA S16_LE, SB S32_LE). Reading both as |
| int16 splits every SB sample into two halves, scrambles channel identity and destroys the |
| spectrum. That bug produced a since-retracted long-range result in this series; see below. |
|
|
| ## Calibration as flown |
|
|
| | | | |
| |---|---| |
| | UMA-16 → camera | `az_offset_deg` **300.87**, `invert_az` true — re-solved this morning from the JBL beacon (spread 0.10°, 41 dB); 1.1° drift from 08-03's 299.77 | |
| | SB-POLARIS → camera | `az_offset_deg` **102.6**, `invert_az` **false** — solved for the first time this morning; two beacons 89.5° apart agreed to 0.9°, run-to-run 0.10°. Rotation only; mic positions are the ring model, not solved. **Nothing consumed SB bearings during this flight** — the cue chain is UMA-only. | |
| | cue producer | cheap daemon (`SUBHUNT=0`); ft16 starves under live tracker load | |
| | site notch | 100–200 Hz (widened from 140 Hz before this flight) | |
| | start pose | pan 45 / tilt 45 | |
|
|
| ## Results |
|
|
| ### Acoustic cue → optical lock |
|
|
| **20 cues posted, 14 locked (70%)**, 11 chirp-rejects, 50 candidates not posted, 26 TRACK |
| episodes. Rotor-band specifically: 10/15 locked. Time-to-lock ranged 1.7–41.3 s. |
|
|
| The site-emitter notch was widened to 200 Hz immediately before this flight, and it worked: |
| **no cue below 222 Hz was posted all session**, where the previous session repeatedly fired |
| false cues on a fixed 140–170 Hz machinery line and slewed the camera at nothing. |
|
|
| ### Where each array loses the drone |
|
|
| Per-second channel-agreement detection in the 240–460 Hz rotor band reads 100% at every |
| range for both arrays — but that number is a trap, because a fixed site harmonic sits inside |
| the band. **The discriminator is the peak-frequency IQR:** a real drone's rotor line wanders |
| with throttle (wide IQR); a fixed emitter is pinned (tight IQR). |
|
|
| | range | UMA-16 peak Hz | SB-POLARIS peak Hz | |
| |---|---|---| |
| | 0–50 m | 342 IQR[319–357] | 312 IQR[258–342] | |
| | 50–100 m | 308 IQR[253–346] | 266 IQR[250–344] | |
| | 100–200 m | 326 IQR[242–348] | 260 IQR[245–324] | |
| | 200–400 m | **245 IQR[240–274]** | **247 IQR[240–263]** | |
|
|
| Both arrays converge on the same pinned ~245 Hz line beyond 200 m — that is the site |
| emitter, not the drone. **Neither array demonstrably hears the drone past ~200 m here, and |
| the SensiBel shows no range advantage over the UMA.** |
|
|
| > **Retraction.** A previous session in this series reported the SensiBel still hearing the |
| > drone at ~330 m while the UMA had collapsed. That came from the int16/S32 misparse noted |
| > above. Recomputed with correct parsing, the SB's long-range IQR is tight and pinned, i.e. |
| > emitter, not drone. Treat any earlier SB-range claim in this series as withdrawn. |
|
|
| ### Optical: the zoom bootstrap trap |
|
|
| The camera held a median of **1.01×** even while tracking, reaching 11.3× at most; 73% of |
| tracked time was still at full wide. Scoring the flight in **pixels on target** (0.35 m |
| drone, GPS slant range, `deg_per_px` from the blackbox) shows why that is decisive: |
|
|
| | range | median px on target | detection rate | px if held at 120 mm | |
| |---|---|---|---| |
| | 0–50 m | 27.1 | **46.6%** | 454 | |
| | 50–100 m | 3.2 | **1.0%** | 88 | |
| | 100–200 m | 1.6 | **0.0%** | 44 | |
| | 200–300 m | 0.7 | 0.0% | 20 | |
| | 300–500 m | 0.7 | 0.2% | 20 | |
|
|
| Detection collapses exactly where apparent size falls below ~10 px, and the pixel model |
| predicts the cliff. The counterfactual column is the finding: at the lens's usable tele the |
| drone would have stayed above the detection floor out to ~300 m instead of dying at 50 m. |
|
|
| It did not, because **zoom is gated on a track that can only exist where zoom is not needed** |
| — zoom climbs only under an established optical track, tracking requires detection, |
| detection requires ~10 px, and inside 50 m the target is already 27 px. Outside 50 m there |
| is no detection, so no track, so no zoom, so there will never be detection. The tracked |
| median range was 10 m. This dataset is a clean instrumented record of that trap. |
|
|
| ## Known issues in this session |
|
|
| * Blackbox logs the zoom *outcome* (`focal_mm`, `zoom_speed`) but not the *decision* — no |
| containment ceiling, no σ, no binding axis. Zoom behaviour can be described from this |
| session but not fully attributed. |
| * SB-POLARIS elevation is not calibrated; azimuth registration exists but nothing consumed it. |
| * `OSD.height` in the decoded CSV is **feet**. |
| * Blackbox sampling is ~2.9 Hz, well below video frame rate. |
|
|
| ## Elevation datum (fit_el_datum, 2026-08-16) |
|
|
| The rig height in this day's drone-altitude frame (the missing constant that |
| floored close-range elevation truth at ~25 deg estate-wide) is SOLVED from |
| this repo's own blackbox TRACK/LOCK poses vs the eval-cache GPS — no |
| acoustics, no field survey. |
|
|
| - **z_rig = -0.50 m**, el = -1 x tilt + 94.36 deg |
| - north offset 50.43 deg (pan sign +1), az gate residual 16.4 deg |
| - med |el residual| **11.25 deg** over 87 camera-on-drone rows, horiz 2-31 m |
| - per band: 0-30m: 11.43 deg (n=86) |
| **SUSPECT** — residual above the clean-day range (0.8-1.9 deg); do not use for close-range el truth until lock purity / pixel-offset is investigated. |
| |
| Artifact: `joshruby/acoustic-knowledge` -> `v3/assets/el_datum/nightjar-flight-20260804.json`. |
| Tool: `sirch613/subhunt-v2` `v3/fit_el_datum.py`. Derive el truth as |
| atan2(hgt - z_rig, horiz) — NEVER from raw hgt. |
| |
