LineGuard finds hotspots on powerlines in radiometric drone photos and gives each one coordinates a technician can drive to. It runs as a background service on a laptop, fully offline, with a dashboard in the browser.

Part of Project Argus by OpenWorks IT.

How it works

1. Fly the line with a radiometric thermal drone (built for the DJI Matrice 4T), camera pointing straight down, photos every few metres with about 80% overlap.
2. Copy the flight folder from the memory card into the inbox (~/LineGuard/inbox), or paste its path into the dashboard.
3. LineGuard finds the conductors in each photo and compares every phase with the other two at the same point. It keeps only the hotspots that appear in most of the overlapping photos that covered them, then places each one on the map.
4. Technicians get a map, a printable report with a QR code per fault, and KML, GPX and CSV files for navigation apps.

Each hotspot is graded on NETA's similar-component bands: possible (1 to 3 °C), probable (4 to 15 °C) and major (over 15 °C). Hotspots that match one from an earlier flight are linked, so the dashboard shows whether a joint is getting worse.

Install (Linux)

Python 3.11 or newer.

pip install git+https://github.com/OpenWorksIT/lineguard
lineguard install-service      # systemd user service + "LineGuard" app launcher
lineguard open                 # dashboard at http://127.0.0.1:8750/

If you'd rather not install the service, run lineguard serve --open in a terminal.

For an offline laptop, download the wheels on a connected machine and copy them across:

pip download "lineguard @ git+https://github.com/OpenWorksIT/lineguard" -d wheels/
pip install --no-index --find-links wheels/ lineguard

Phone app and driving to faults

The LineGuard app (app/) runs on Android and iOS. Technicians use it to drive to each hotspot, with an arrow, the distance and spoken prompts. It works offline once a flight is open on the phone.

It connects in one of two ways:

• To the laptop in the vehicle, over Wi-Fi. Run lineguard install-service --share, and lineguard hotspot if there's no other Wi-Fi.
• To a hosted LineGuard, over mobile data.

To pair a phone, choose Connect a phone in the dashboard. Pairing codes last ten minutes and work once. Paired phones can be unpaired from the same panel.

Without a password, the laptop's own browser needs no login. Every other device must be a paired phone. The dashboard answers only to IP addresses and localhost; if you open it by another name (for example bakkie-laptop.local), add that name to allowed_hosts.

To publish the app in Google Play and the App Store, see app/store/README.md. The latest security review and its fixes are in docs/security-audit-2026-10.md.

Tower numbers

Each hotspot is labelled with the nearest tower, for example "Tower T44, Collector A 33 kV line". The data comes from two sources:

• OpenStreetMap, the data behind openinframap.org. When the laptop is online, power lines, towers and substations around each flight are fetched once through the Overpass API and kept with the flight.
• Your own tower register. Wind-farm 33 kV collector lines are rarely mapped in OpenStreetMap, so import your own list in the dashboard under Tower list. It takes a CSV of ref, lat, lon[, line], or KML or GeoJSON points, and works offline.

Map and power data © OpenStreetMap contributors (ODbL).

Hosting it for remote testing

deploy/vps/ runs LineGuard as a Docker container behind an existing Caddy, with a login and browser uploads instead of the local inbox. See deploy/vps/README.md.

Try it without a drone

lineguard demo                          # a simulated 500 m, 33 kV flight lands in the inbox
lineguard demo --scenario 33kv_hot      # the same line on a hot afternoon

The service picks the flight up within a few seconds. The planted faults are saved in the flight folder as _truth.json, so you can check what was found against what was planted.

Real flights (DJI Matrice 4T)

Decoding temperatures. DJI's R-JPEG photos are decoded with dji_irp, part of the DJI Thermal SDK. The SDK can't be bundled with LineGuard, so download it from DJI and point LineGuard at the tool:

# ~/.config/lineguard/config.toml   (create a template with: lineguard init-config)
dji_irp = "/opt/dji_thermal_sdk/utility/bin/linux/release_x64/dji_irp"

[detection]
standoff_m = 20.0     # distance from camera to conductors that the route is flown at

Flight settings LineGuard expects:

• Gimbal pitch -90° (straight down). Photos pitched more than 10° from straight down are skipped.
• Camera heading following the route, so the conductors run up the photo.
• Thermal photos saved as R-JPEG, by distance interval, with about 80% front overlap.
• RTK fix. On sites with no mobile signal, use a local base station such as the D-RTK 3.
• Fly when the ground is cool (morning, overcast). Sun-heated ground hides small faults on thin conductors.

Position and heading come from each photo's XMP data. Any matching wide photo (_W.JPG) is used for a colour close-up.

Offline maps

Hotspot coordinates never need a network. The map background does. To have one offline, put tiles in ~/.local/share/lineguard/tiles/{z}/{x}/{y}.png (any XYZ tile set you're licensed to use, e.g. made with QGIS's "Generate XYZ tiles") and LineGuard serves them itself.

Settings

Everything is optional. These are the defaults:

Setting	Default	Meaning
host, port	127.0.0.1, 8750	Dashboard address. Keep it on localhost unless the network is trusted.
inbox_dir	~/LineGuard/inbox	Folders copied here are processed automatically.
data_dir	~/.local/share/lineguard	Database, close-ups, offline tiles.
dji_irp		Path to the DJI Thermal SDK's dji_irp tool.
tiles_url	OpenStreetMap	Online map tiles, used when no offline tiles exist.
allowed_hosts		Extra names the dashboard may be opened by, comma separated.
public_url		Hosted only (required): the https address phones and browsers use (LINEGUARD_PUBLIC_URL).
behind_proxy	false	Hosted behind Caddy: take each client's address from X-Forwarded-For so login limits apply per client. Only when the proxy is the sole way in.
password		Requires a login (12 characters or more). Always set when hosted.
[detection] standoff_m	20.0	Camera-to-conductor distance. The laser range is used instead when it plausibly hit the line.
[detection] threshold_c	3.0	Minimum rise over the other phases to flag.
[detection] phases	3	Conductors expected side by side in each photo.
[camera] diagonal_fov_deg	45.0	Thermal camera field of view (Matrice 4T).

Other cameras

Any camera that can export per-pixel temperatures works through the generic format: one name.npy array (°C) and one name.json per photo, holding lat, lon, yaw_deg and optionally pitch_deg, range_m and taken. See lineguard/readers/generic.py.

Limits of this first version

• Straight-down views only, with the phases side by side (horizontal configuration). Vertical and delta configurations need an oblique view and aren't supported yet.
• The detection is tested on simulated flights, not real ones yet. Thresholds will be tuned on the first real flights.
• The dji_irp command line follows the Thermal SDK's sample tool. Check it against the SDK version you install.
• The colour close-up is cut from the wide photo by field-of-view geometry, so its framing is approximate.

Development

pip install -e ".[test]"
pytest

Layout: readers/ (DJI and generic photos), detect.py (the method), pipeline.py (one flight end to end), worker.py (inbox watcher), web.py with templates/ and static/ (dashboard), demo_scene.py (the flight simulator used by the demo and the tests).

The dashboard uses Leaflet (BSD-2-Clause), bundled in lineguard/static/vendor/leaflet.

Licence

LineGuard is free software, © 2026 OpenWorks IT (Pty) Ltd, licensed under the GNU Affero General Public License v3.0 or later. You may use, study, change and share it. If you run a modified version for others over a network, you must offer them its source (set source_url so the dashboard and app link to it).

NOTICE lists:

• an extra permission that lets the phone app be distributed through app stores;
• the names and logos, which stay with OpenWorks IT releases;
• the DJI Thermal SDK, which isn't part of LineGuard;
• the third-party components.