GPS Whistle
Whistle your location into any recording. It survives compression and can be decoded later.
Start your recorder, hold this device near it, turn the volume up, and press the button. It plays a short tune and some chirps, twice: about 10 seconds, or 14 with an author name.
Open a recording (voice memo, field recording, video) to find any GPS Whistle in it. Nothing is uploaded; decoding happens on this device.
How it works, and what it proves
The page encodes a 40-byte frame as audible tones, framed by a tiny melody that spells G‑P‑S‑W in notes (G–B–E–B, by the French method Ravel and Debussy used to spell HAYDN) and plays it backwards at the end, using ggwave, with Reed–Solomon error correction and a CRC-32 check. The frame carries the location on a ≈19 m grid (or snapped to a fixed ≈5 km grid in Coarse mode, or nothing in Off), the reported accuracy, a UUIDv7 (which includes the time), optionally 8 bytes of the current drand randomness beacon, and optionally an author name (up to 24 bytes of UTF-8, which lengthens the frame to 64 bytes and adds about 2 seconds to each play). It plays twice.
In testing, it decoded through AAC, MP3 and Opus compression, generation loss, resampling, 8-bit audio, heavy noise, room reverb, clipping, automatic gain control, and recorders whose clocks run up to 4.5% fast or slow.
- Private by default. Your location never leaves this device. Fetching drand sends nothing about you. Timestamping sends only a SHA-256 hash of the record.
- Time window. Your device’s clock can say anything, so the claimed time alone proves nothing. The drand value is a public random number that nobody could know in advance; having it in the whistle proves the whistle, and any recording containing it, was made no earlier than that moment. It’s like holding up today’s newspaper in a photo. It shows the recording is fresh, not prepared in advance. An OpenTimestamps proof of the saved record (or of the recording file itself) proves it existed no later than a Bitcoin block. Together they pin the recording inside a time window.
- Author: the name is a notice, shown with ©, not a signature. Anyone can type a name.
- What it doesn’t prove: that anyone was actually there. Browser locations can be faked, and anyone can play a whistle into any recording. It’s provenance metadata that’s hard to strip, not proof of presence.