| --- |
| license: cc-by-4.0 |
| task_categories: |
| - object-detection |
| - audio-classification |
| tags: |
| - drone-detection |
| - counter-uas |
| - acoustic-array |
| - ptz-tracking |
| - multimodal |
| - gps-truth |
| - low-altitude |
| pretty_name: "nightjar field flight 2026-08-04 #4 — longest tracked sortie of the day" |
| --- |
| |
| # nightjar flight — 2026-08-04, fourth sortie |
|
|
| Last sortie of a four-flight day, and **the one with the most time under an optical track**. |
| Same rig and site as the other 2026-08-04 sessions. GPS truth: **3,572 valid UTC stamps of |
| 3,573**. |
|
|
| | | | |
| |---|---| |
| | airborne | 357 s | |
| | max height | 26 m | |
| | max slant range | 244 m | |
| | median elevation angle | **5°** | |
| | path flown | 894 m | |
|
|
| ## The interesting number |
|
|
| **53 cue candidates, and 43 of them were evaluated at the 14.6 dB threshold.** The deployed |
| presence gate is state-dependent — strict (14.6 dB) while nightjar reports TRACK, relaxed |
| (10.0 dB) while it is searching — so a candidate stamped 14.6 means the tracker *was locked at |
| that moment*. Only 10 candidates saw the relaxed threshold. Compared with the third sortie, |
| where all 8 candidates were at 10.0 dB and the tracker was never locked when a cue was |
| evaluated, this session spent substantially more of its life holding a track. |
|
|
| That is a suggestive contrast, not a controlled one: the two sorties differ in duration |
| (357 s vs 200 s), range (244 m vs 142 m) and path length (894 m vs 357 m) as well. |
|
|
| `audio/cue_log.jsonl` stamps `thr_db` and `nj_state` on every candidate, so each cue is |
| attributable to the threshold in force. 4 chirp-rejects. Two `start` records appear because |
| the cue daemon was restarted into the session after a device-contention race at launch (the |
| daemon *is* the UMA recorder — the array is single-open). |
|
|
| ## Caveat that applies to the whole day |
|
|
| ⚠ **26 m altitude at 244 m range is a ~5° elevation angle** — the drone was on the treeline, |
| against foliage rather than sky. Three of the day's four sorties flew this profile. It is a |
| hard background for the detector and it sits at the null of a horizontal array's elevation |
| response (sensitivity goes as sin(el), so ~0 at the horizon). The 50–150 m detection question |
| that motivated the day's work therefore remains unexercised. |
|
|
| ## Contents / gotchas |
|
|
| ``` |
| audio/uma16_<epoch>.wav UMA-16, 16 ch, S16_LE audio/sb_<epoch>.wav SB-POLARIS, 8 ch, S32_LE |
| audio/cue_log.jsonl cue gate log (thr_db, nj_state per candidate) |
| video_segments.tar 1080p native + 768x432 substream, 60 s MPEG-TS |
| blackbox/state.jsonl tracker FSM ~2.9 Hz blackbox/frames.tar 2,856 stills f<epoch_ms>.jpg |
| dji/*.csv, *.txt decoded + original FlightRecord (CUSTOM.dateTime = true UTC) |
| ``` |
|
|
| 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; detect them by RMS (live ~−70 dBFS, dead ~−190) rather |
| than hardcoding. ⚠ **The arrays use different sample widths** — UMA S16_LE, SB S32_LE; reading |
| both as int16 scrambles SB channel identity and destroys its spectrum. |
|
|
| Calibration as flown: `az_offset_deg` **301.37**, `invert_az` true. Cue producer: cheap daemon |
| (`SUBHUNT=0`). Site notch 100–200 Hz. Start pose pan 178.9 / tilt 45, pointed at the JBL |
| beacon. Cue-gated blob seeding was present in the build but **disabled** for this flight. |
|
|
| ## GPS-referenced pixel work |
|
|
| Placing the drone in the image from GPS reaches a floor of about **5° of bearing error** on |
| this rig's data — the DJI's own ±2–5 m of position is 4–9° of bearing at the 20–45 m ranges |
| where the optical correspondences live. Treat any in-frame or pixel-level claim derived from |
| GPS here as approximate. |
|
|
| ## 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 = +1.70 m**, el = -1 x tilt + 75.38 deg |
| - north offset -64.56 deg (pan sign -1), az gate residual 3.4 deg |
| - med |el residual| **1.10 deg** over 187 camera-on-drone rows, horiz 12-14 m |
| - per band: 0-30m: 1.10 deg (n=187) |
| |
| Artifact: `joshruby/acoustic-knowledge` -> `v3/assets/el_datum/nightjar-flight-20260804-4.json`. |
| Tool: `sirch613/subhunt-v2` `v3/fit_el_datum.py`. Derive el truth as |
| atan2(hgt - z_rig, horiz) — NEVER from raw hgt. |
| |
