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research/transjakarta-live-data/methodology.md
hermes 3a518be39f Add transjakarta-live-data research topic 
Verified TransJakarta realtime stack: anonymous MQTT bus feed (wss://mqtt.tj.co.id:8084/mqtt), guest REST API (tijeapi.transjakarta.co.id), official GTFS. Cross-capture verification vs third-party tracker, connection recipes, snapshot tool.
2026-10-12 09:34:23 +00:00

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Methodology — how this was verified

Repeatable procedure (executed Oct 11–12, 2026). Tools: curl, node (packages ws, mqtt), jq.

Steps

  1. Map the target: fetch the site's HTML + JS bundles with curl; read the CSP header (connect-src names allowed WebSocket endpoints); grep bundles for protocol strings → found oyenza's own WS (/api/live) and its message types (hello/feed/snap/delta).
  2. Find static-data citations: static.json referenced the official GTFS zip URL → static layer source identified.
  3. Find the upstream: search GitHub for projects in the same ecosystem (tj-live, open-tj) → they document the REST + MQTT + GTFS stack.
  4. Simultaneous cross-capture:
    • oyenza-ws.mjs — WS client on wss://transit.oyenza.com/api/live
    • mqtt-cap.mjs / mqtt-long.mjs — MQTT client on wss://mqtt.tj.co.id:8084/mqtt, subscribing /mobile_armada/#
    • Analysis with compare.mjs / compare2.mjs (ID sets, field agreement, position deltas), seg1.mjs (topic segments), mqtt-rate.mjs (rate profile).
  5. Decode the topic grid: four POST /v1/bus probes at ±0.1° offsets → index-shift mapping (≈0.01°/unit).
  6. Cadence check: re-connect to oyenza's WS and record delta intervals (oy2.mjs) → exactly ~3.00 s.

Key results

  • 1,794 common buses; 100% trip/route ID match; median position delta 8.9 m; p90 42 m; 97.8% fleet overlap (75 s window).
  • Broker: ~2,000+ retained messages instantly on subscribe; per-bus refresh ~8–75 s in samples.
  • oyenza deltas: 3000–3013 ms gaps, ~1,000 position records each.

Artifacts

  • All scripts + raw captures archived at workspace/transjakarta-live-captures/ (4.6 MB): oyenza page + bundles, oyenza WS captures, MQTT captures, comparison outputs, rate profiles, tije REST responses (guest token redacted).
  • Scratch copies live under ~/.hermes/profiles/research/cache/scratch/oyenza/ (auto-pruned after ~24 h idle — use the archive instead).
  • Reusable snapshot tool: transjakarta-live-data/scripts/tj-snapshot.mjs