slopes-creations · ATC labs

6Tools designed, built and documented

11Pages in the ATC Toolkit workstation

24Engineering issues logged and fixed

14ATC information areas reviewed

3Third-party decoders integrated

4Receivers integrated

01 · System overview

The signal chain

Three small programs sit between the receivers and the display. One SDR stick can only tune one frequency, so ADS-B and the radio side run on separate receivers. Click any box for its full details.

Surveillance (ADS-B) Datalink Audio To the display

02 · Decode lab

Inside a 1090 MHz message

This is what dump1090 hears and what the toolkit ends up showing. An ADS-B identification message is 112 bits: who is sending, what kind of message it is, the callsign packed into 6-bit characters, and a 24-bit parity check. Type a callsign, then click any bit to flip it and watch the parity check catch the error.

DF17 extended squitter, identificationvalid

Callsign (A–Z, 0–9, up to 8) ICAO address (hex)

0 bits flipped

Decoded fieldshover a row

Encoder checked against a published reference message from an open ADS-B textbook (Sun, The 1090 MHz Riddle): identical output and parity.

03 · Safety nets

Break the separation

The toolkit's Analyse page checks safety nets. This demo shows the idea behind short-term conflict alert: project both tracks forward, find the closest point of approach, and alert if both the horizontal and vertical minima would be broken inside the look-ahead time. Drag the sliders until it alarms. It is an illustration, not the EUROCONTROL STCA specification.

Conflict probe, simulatedt = 0 s

CLEAR

Controlslive

Horizontal minimum 5.0 NM Vertical minimum 1000 ft Look-ahead 120 s SIM202 level FL250 SIM202 heading 270° Speed ×8

CPA in–

Miss distance–

Vertical–

Range now–

SIM101 holds FL250 heading 090 at 420 kt. SIM202 flies at 400 kt on the heading and level you set.

04 · The tools

What each one does, hands on

TOOL 01ATC_Toolkit_v5.html

ATC Toolkit

A complete surveillance workstation in a single web page, about 580 KB with no install. It plots aircraft in 2D radar or 3D airspace view, colours each label by its ASTERIX source, and opens an identity card when you click a track.

Input: Live SBS feed over WebSocket, PCAP or raw ASTERIX files, or generated scenarios
Output: Map picture, analysis reports, exports to CSV, SBS, JSON, ASTERIX, GeoJSON and KML
Diagnostics: Global error capture (window errors, promise rejections, render errors) into a downloadable log
Why: Lets one engineer test, replay and inspect surveillance data without an operational system

Decode page, simulatedclick a track

ADS-BSSR / Mode SMLAT / WAMSystem trackEmergency

DecodeLive map, 2D or 3D, ID cards
GenerateSynthetic traffic and scenarios
PCAPASTERIX files, SAC/SIC, A/B compare
AnalyseCoverage, data quality, safety nets, FRUIT
ToolsConverters, self test, import and export
SDR ADS-BWaterfall, MLAT solver, diagnostics log
Voice SDRAirband scanner and networked receiver audio
NetworksFeed and share status
WeatherMETAR, QNH, TAF, SIGMET
DatalinkACARS, VDL2, AFTN and AMHS decode
networked receiverReceiver source, tuning, bridge log

TOOL 02receiver_bridge.py

Receiver bridge

The translator in the middle. It takes whatever the receivers produce (dump1090's SBS stream, decoder JSON over UDP, or receiver MQTT spots), converts it into the one SBS format the toolkit understands, and serves it on a WebSocket. It also carries control commands back to the networked receiver to tune it.

Input: --sbs, --json-udp, --mqtt, --control
Output: SBS lines on a local WebSocket
Checked by: Built-in --selftest for the conversion logic

Try the conversion: edit the JSONok

Each JSON message becomes one SBS line per message type, in the 22-field BaseStation order. Hover any field to see its name. Illustrative only: the real bridge's field mapping lives in receiver_bridge.py.

TOOL 03audio_bridge.py + networked receiver embed

Airband voice

Lets you listen to the 118 to 137 MHz AM airband inside the toolkit. A second USB stick runs rtl_fm and the audio bridge turns it into a network audio stream; the networked receiver in VHF mode adds a live waterfall and audio panel.

Input: airband USB stick via rtl_fm, or the receiver's own page
Output: /audio.wav?f=123450000 on a local audio port
Hardening: Frequency, mode and gain from the URL are validated; bad values get HTTP 400 (fix E22)
Limit: One listener at a time; the ADS-B stick stays on ADS-B

Waterfall, simulated 118–137 MHzclick to tune

123.450

Squelch

CLOSED

/audio.wav?f=123450000

TOOL 04setup_vdl2.sh + run_datalink.sh

Datalink kit

Scripts that build and run the VDL2 and ACARS decoders on a single-board computer, then send their messages as JSON to the bridge. HFDL comes from the networked receiver, which decodes on the device. ACARS carries text, not a position, so these messages appear in the Datalink page rather than on the map.

Modes: VDL2, ACARS (VHF 131–137 MHz), HFDL (HF)
Decoders: dumpvdl2 (Hz), acarsdec 3.x (-j host:port), dumphfdl (kHz)
Route: Board to PC as JSON over UDP, or MQTT from the networked receiver

Message feed, simulatedclick a message

TOOL 05serve_toolkit.py + start_all.bat

Toolkit server and launcher

A small web server using only Python's standard library. Serving the page over http rather than opening it as a file removes browser security blocks, and its weather proxy fetches METAR and TAF from an allow-listed set of hosts. The launcher asks which ADS-B source you have and starts everything in the right order.

Serves: This computer only, unless started with --lan
Proxy: GET /wxproxy?url= for 2 allow-listed public weather and aircraft-data services only; others get 403
Why: Fixes the "Failed to fetch" weather error at its root (E2)

Start sequence

TOOL 06atc-coverage-review

ATC coverage review

A structured gap review for any ATC system, simulator, test facility or test procedure. It walks fourteen information areas, ties each gap to the standard that governs it (ICAO, EUROCONTROL, UK CAA CAP 670, Military Aviation Authority) and states plainly which standards were actually checked and which were not.

Answers: "Am I missing anything?" and "Which standard covers this?"
Output: Prioritised gap list with a status label per standard
Rule: An unverified claim shown as fact counts as a defect

The fourteen areasclick a letter

05 · Engineering log

24 problems found and fixed

Every issue hit while integrating real receivers on Windows 11 and a single-board computer, with its root cause and fix. Search it or filter by component.