Kafila — Convoy Tracking for Zero-Signal Terrain

The Problem

Off-road convoys lose each other, and cell towers don't help

Group off-road trips through Northern Pakistan routinely cover terrain with no cellular signal for hours at a stretch — mountain passes, riverbeds, forest tracks. Vehicles spread out, someone takes a wrong turn, and there's no way to know who's where until everyone happens to regroup at the same waypoint. WhatsApp location sharing simply stops working the moment signal drops, which is exactly when you need it most.

The requirement wasn't "build a tracking app" — plenty exist. It was build one that keeps working when the network doesn't, and that syncs cleanly the instant a bar of signal reappears.

What I Built

A convoy app that assumes the network will fail

Kafila is a installable PWA where every vehicle's phone queues its own GPS trail locally and pushes it to the group the moment connectivity allows. The map (MapLibre GL over free Protomaps vector tiles) shows live positions, trails, and distance travelled for every member of the convoy, plus SOS alerts, waypoint checkpoints, geo-tagged trip notes, and refuel logging.

A public no-login "watch" link lets family back home follow the convoy live without an account — important for trips where the whole point is that someone worries.

Post-trip analytics for a completed convoy trip — speed profile, elevation profile, and a time-at-speed breakdown, reconstructed entirely from the queued GPS trail.

Technical Highlights

Built around one hard constraint: no signal, no problem

Offline-first GPS queue

Every position reading lands in a Dexie (IndexedDB) queue first. A sync engine drains it to the server the moment connectivity returns — nothing is lost to a dead zone.

Polling, not WebSockets

Hostinger shared hosting doesn't support WebSockets, so live updates run on exponential-backoff polling instead — a constraint that shaped the whole real-time layer.

GPS throttling that still looks smooth

Points are queued at most once per 3 seconds and only after ≥5m of movement (with a 30s heartbeat for parked vehicles) — cutting row volume ~70% with no visible loss on the trail.

iOS background workarounds

iOS suspends JS when the screen locks, so there's no reliable background GPS. Kafila re-acquires a wake lock on visibility change and falls back to periodic polling, with a clear on-screen warning when tracking isn't guaranteed.

Garmin MapShare integration

For satellite communicators, a cron job polls Garmin's MapShare KML feed so off-grid members without a phone signal still appear on the same live map.

Public watch link, no login

A session-tracked, unauthenticated `/watch/:code` route gives family a live view of the convoy — deliberately friction-free for people who aren't part of the trip.

Stack

Under the hood

Frontend	React 18 + Vite + Tailwind + Zustand, installable PWA
Maps	MapLibre GL JS + Protomaps vector tiles (free, no rate limits at this scale)
Offline	Dexie.js (IndexedDB) GPS queue with a persistent sync engine
Backend	PHP 8.1 + MariaDB on Hostinger shared hosting
Media	Cloudinary (alert/POI photos), SendGrid (SOS email)
Auth	JWT with access + refresh token rotation

Status

Where it stands

Phase 1 — auth, convoy creation/joining, live GPS tracking, and the map — is complete and live, and post-trip analytics (speed, elevation, time-at-speed) already ships too. Phase 2 (messaging, SOS, checkpoints, Garmin) is backend-ready; POIs and trip replay are planned for future trips.

Kafila (قافلہ) — convoy tracking for zero-signal terrain

Off-road convoys lose each other, and cell towers don't help

A convoy app that assumes the network will fail

Built around one hard constraint: no signal, no problem

Under the hood

Where it stands

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