Skip to content

VLF Radio Source Feasibility

This document consolidates feasibility findings, receiver stations, endpoints, acquisition/capture manifests, and coverage status for Italy-relevant Very Low Frequency (VLF) radio data.

1. Core Feasibility Findings

  • VLF.it Homepage: Reachable over HTTP, serving as a static library of articles and amateur radio experiments, rather than a documented web service. Open Lab guidelines allow non-commercial use, but commercial rights are reserved by the authors.
  • Cumiana Station: Confirmed machine-fetchable live spectrograms (JPEG) and status summaries.
  • Abelian Natural Radio: Exposes Cumiana Ogg streaming and a retrieval PHP form. However, early probes returned zero usable bytes, and the archive returns no database errors.
  • Modeling Readiness: Image-derived parameters are used as proxy features until raw waveforms or numeric trace endpoints are established.

2. Cumiana VLF Monitoring Station

  • Location: Cumiana, Torino, NW Italy (44.95609 N, 7.42123 E approximate)
  • Maintainer: Renato Romero / Openlab
  • Page: http://www.vlf.it/cumiana/livedata.html (requires curl --http1.1 --raw configuration).

Live Spectrogram Endpoints

Spectrogams are updated roughly every 30 or 60 minutes:

Endpoint ID URL Content Cadence
last_E_VLF http://www.vlf.it/cumiana/last_E-VLF.jpg Last 8 hours vertical electric-field spectrogram (Marconi antenna) 30 mins
last-geomar http://www.vlf.it/cumiana/last-geomar.jpg Geophone (1–30 Hz) + electric-field (1–105 Hz) spectrogram 30 mins
last-marconi-multistrip-slow http://www.vlf.it/cumiana/last-marconi-multistrip-slow.jpg Electric-field daily multistrip (110s scroll) 30 mins
last-geophone-multistrip-slow http://www.vlf.it/cumiana/last-geophone-multistrip-slow.jpg Geophone daily multistrip (4.6s scroll) 60 mins
last-plotted http://www.vlf.it/cumiana/last-plotted.jpg Last 30 hours of plotted traces 30 mins

3. Abelian VLF Archive and Live Streams

  • Live Stream: http://abelian.org/vlf/live-stream.php?stream=vlf15 (Cumiana live Ogg stream).
  • Archive Form: http://abelian.org/vlf/retrieve.php
    • Parameters: ts (UTC start, YYYY-MM-DD HH:MM:SS), len (seconds, 0.05 to 120.0), vlf15=on (Cumiana filter), format (wav, vt, sg, td).
  • Findings: Archive requests submitted for June/July 2026 timestamps returned HTTP 200 but were empty, reporting no database and declaring download size 0. Do not rely on historical Abelian data until a nonempty download is successfully verified.

4. Ingestion and Capture Manifest

The Cumiana image capture pipeline is configured via: * Manifest Path: data/raw/vlf/cumiana/manifest.csv * Storage Directory Structure: 

data/raw/vlf/cumiana/captures/YYYY-MM-DD/<endpoint_id>_<last_modified_utc>.jpg
data/raw/vlf/cumiana/captures/YYYY-MM-DD/<endpoint_id>_<last_modified_utc>.metadata.json
Filenames replace colons with hyphens. The .metadata.json stores the response headers (Date, Last-Modified, ETag, Content-Length, Content-Type).

Capture Rules

  • Do not overwrite existing files with the same timestamp.
  • Politely respect the cadence (poll no faster than every 30 or 60 minutes).
  • The supervised loop command rejects repeated runs under 60 seconds.

5. Feature Extraction and Coverage

Because raw waveforms are not yet available, we extract proxy features by cropping and analyzing the Marconi spectrogram JPEG pixels.

Extracted Image Features

  • Overall availability and stale/missing flags for each window.
  • Mean and variance within specific cropped time-frequency bands.
  • Hot-color ratio and vertical streak count (indicator of impulse noise or sferics).
  • Simple anomaly scores relative to the running baseline of the past week.

Table Coverage Status

  • Historical June Labeled Windows: Have quality_missing_vlf=1 since active image captures only began after those windows.
  • Prospective Labeled Windows: Rebuilt image-window tables (e.g. central_italy.prospective_vlf_image_windows.labeled.csv) contain 247 consecutive rows starting from 2026-06-29, with 0 missing VLF image features.
  • We use the update-prospective-vlf-table script to periodically append new rows on a systemd timer.

6. Acquisition and Verification Commands

Record short live audio stream from Abelian: 

PYTHONPATH=src python3 -m elfquake.cli record-vlf-abelian-cumiana --duration-seconds 10 --max-bytes 1048576

Request and retrieve an Abelian archive WAV segment: 

PYTHONPATH=src python3 -m elfquake.cli fetch-vlf-abelian-cumiana-archive --start 2026-07-05T10:38:11Z --duration-seconds 5 --format wav

Audit the Abelian archive database for availability: 

PYTHONPATH=src python3 -m elfquake.cli probe-vlf-abelian-cumiana-archive --start 2026-07-05T10:38:11Z --duration-seconds 0.05 --format wav --out data/derived/vlf/abelian_cumiana_archive_probe.csv

Extract visual features from a folder of captures: 

PYTHONPATH=src python3 -m elfquake.cli extract-vlf-image-features --image-root data/raw/vlf/cumiana/captures --out data/derived/multimodal/cumiana_last_E_VLF.image_features.csv