nodecode-doppler-geo
Aircraft Doppler Geolocation: finds the flyover tones in a recording and estimates where it was made. A Nodecode rewrite of mojomast/hermes-aircraft-doppler-geolocation by mojomast.
A plane passing overhead leaves a faint tone in the spectrogram that falls away either side of closest approach. How far it drops is the plane's speed; how sharply is how near it passed. Two tools read that:
| Tool | What it answers |
|---|---|
doppler_detect |
The flyovers in a WAV file: closest approach, speed, slant distance, rest tone, fit residual. Offline. |
doppler_locate |
The ground area they and an ADS-B track CSV agree on: best point, top 5, 68/95% areas, a confidence flag. |
Get it
Tell the agent "add the doppler-geo cell", or run nodecode add nc://doppler-geo.
Set it up
Nothing is required to detect. doppler_locate reads ADS-B from a CSV you
give it, with time_s in the recording's own clock:
icao,time_s,lat,lon,alt_ft abc123,0.0,51.5071,-0.1200,984.3
Point the tracks member of the doppler-geo section at one file (it is then
the default for every call), or name one per call. The rest of the section has
defaults that hold: fmin 60, fmax 400, max_events 3, sigma_hz 2,
sound_speed 343.
Only RIFF/WAVE is read (PCM 8/16/24/32 or 32-bit float, any channel count).
Convert anything else first: ffmpeg -i clip.mp4 -ac 1 -ar 8000 clip.wav.
Use it
Ask in words — "find the flyovers in this recording" — or type:
/doppler clip.wav— the flyovers./doppler locate clip.wav 51.5,-0.12,4— the area, within 4 km of that point.
From eval the same two are (doppler-geo:detect "clip.wav") and
(doppler-geo:locate "clip.wav" "51.5,-0.12,4").
Read the confidence first. ok needs a posterior that concentrates and a fit
under 2 Hz; a low result is a search region, not a point. Over water and
away from ADS-B coverage there are no tracks to score at all.
What it does not do
The original fetched its own ADS-B: a day of adsb.lol history, about 3 GB
streamed per uncached day, cropped to the region and cached, plus Copernicus
DEM tiles and Open-Meteo temperature. This cell reads the tracks you hand it
and takes ground elevation as sea level. It has no broadband (ground-reflection
jet) mode, no PNG plots, no ffmpeg. See NOTICE.
License
MIT. The method and the original implementation are Copyright (c) 2026 Kyle
Durepos: see LICENSE and NOTICE.
