ADR-0001 — Build a DIY system instead of using a commercial tracker

Status: Accepted · Date: 2026-06-14

Context

The goal is real-time player data that the coach fully owns, affordable for ~10 youth players. The market (see market-analysis) shows: - Consumer trackers are closed (proprietary BLE, encryption, store-and-sync to vendor cloud) and can't be read from outside. - Public APIs exist only on a few pro brands and are cloud APIs (customer + token), not device SDKs. - Affordable youth devices (Footbar, STATSports Athlete) are the closed ones; the ones with APIs (Catapult, WIMU) are expensive subscription/pro systems. Cheap + open don't coexist. - Every real-time commercial system is closed.

Decision

Build a custom system: per-player WiFi wearable + owned backend + owned coach UI ("Path A").

Consequences

• + Full real-time stream, complete data ownership, one-time cost, no subscription.
• + Backend/UI are in the owner's wheelhouse (full-stack).
• − Must build firmware and durable wearable units; pitch calibration is on us.
• − Consumer-GPS accuracy (~2–5 m), not elite-grade.

Alternatives considered

• Buy commercial (Footbar/STATSports/Catapult/PlayerMaker) — rejected: closed data and/or per-player subscription, and the cheap ones aren't real-time/open.
• Path B — cheap 4G trackers + Traccar (open source) — viable weekend MVP for live dots, but ~1 Hz, GPS-only, 1–3 s latency; too coarse for sprint/accel/load. Kept as a fallback to see live dots fast.