Live Military Grid Reference System coordinates with 1-meter precision. GPS Kalman filter for smooth, accurate position tracking. MGRS grid overlay on offline maps from GZD down to 100m resolution. Bearing, distance, dead reckoning, resection, pace count (with accelerometer step detection), declination, and coordinate conversion tools. NATO phonetic voice readout for hands-free grid calls.

Zero-config proximity sync over BLE + WiFi Direct (Android) / AWDL (iOS). Devices within range automatically discover each other and share encrypted position and marker data. No internet required. No pairing codes. No servers.

• 2-8 devices per session
• AES-256-GCM encryption with ECDH P-256 ephemeral session keys
• Tiered session security: Open, PIN, or QR code authentication
• Delta payloads under 200 bytes per position update
• Ghost markers with time-decay visualization when teammates disconnect
• Velocity vectors project last-known movement direction
• Expedition Mode: <3% battery/hr (BLE-only, 30s updates)
• Ultra Expedition Mode: <2% battery/hr (BLE-only, 60s updates)
• Auto-reconnect with exponential backoff on disconnect

Download map packs from USGS Topo (public domain) and OpenTopoMap for full offline operation. Maps are cached locally as MBTiles with MGRS grid lines rendered as a dynamic overlay.

One engine, four presentation layers. Terminology, icons, and quick actions adapt to your mission:

• Search & Rescue -- sector assignments, clue markers, search patterns
• Backcountry -- camp, waypoint, and trail navigation
• Hunting -- stand locations, game sightings, property boundaries
• Training -- exercise objectives, rally points, phase lines

Dead Reckoning, Resection, Pace Count, Bearing/Back Azimuth, Coordinate Converter (MGRS/Lat-Lon/DMS/UTM), Range Estimation, Slope Calculator, ETA/Speed Calculator, Magnetic Declination, Celestial Navigation, MGRS Precision Reference.

One-tap PDF export: map snapshot, mission timeline, track data, timestamps, team roster, markers, and session log. Share via AirDrop, file share, or any local transfer.

Red Light (night vision, free), NVG Green (Pro), Day White (Pro), Blue Force (Pro).

Open Red Grid Link and your MGRS position appears on the offline map. Navigate using bearing, distance, and dead reckoning tools -- identical to Red Grid MGRS but with a full map view and 11 tactical tools.

1. Start a session -- tap one button to begin broadcasting over BLE
2. Set security -- choose Open, PIN, or QR code authentication
3. Teammates appear -- any device running Red Grid Link within range (~50-100m open, 20-60m woods) is automatically discovered
4. Positions sync -- AES-256-GCM encrypted delta updates flow between all devices at configurable intervals
5. Ghosting -- if a teammate moves out of range, their last-known position remains on your map with time-decay opacity (100% to outline over 30 minutes)
6. Reconnect -- when a ghost comes back in range, their marker snaps to live position

No accounts. No servers. No cell service. No configuration. It just works.

Pricing:

• Free -- All modes, 2-device Field Link, 1 map region, Red Light theme
• Pro -- $3.99/mo or $29.99/yr
• Pro+Link -- $5.99/mo or $44.99/yr (Pro + full 8-device Field Link)
• Team -- $199.99/yr (8 seats, includes Pro+Link for all members)
• Lifetime -- $99.99 one-time (Pro+Link forever)

No accounts. No analytics. No ad networks. No third-party data SDKs. Privacy-safe crash reporting (Sentry, release mode only — no location data transmitted). In-app purchases processed by Apple/Google -- Red Grid Link never sees your payment details. Full details in PRIVACY.md.

git clone https://github.com/RedGridTactical/RedGridLink.git
cd RedGridLink
flutter pub get
flutter pub run build_runner build --delete-conflicting-outputs
flutter run

Requires Flutter SDK. Currently targeting iOS -- Android support is planned. All free features work from source. Pro features require a valid purchase through Apple. Field Link requires Bluetooth and location permissions on physical devices.

Full roadmap with feature checklists: ROADMAP.md

• Security audits and cryptographic library updates
• Battery performance optimization
• Map tile source expansion
• Test coverage expansion (target 90%+)
• Store listing optimization and A/B testing

Red Grid Link is built in the open. We welcome bug reports, feature requests, and pull requests.

See the Roadmap for planned features and where help is needed.

MIT + Commons Clause -- free for personal non-commercial use. Commercial and organizational deployment requires written permission.

Contact: [email protected]

Your team. Your grid. No cell towers required.

If Red Grid Link helps you stay coordinated in the field, give it a star and share it with your team.