Maps that
work where
you go

Topographic mapping with 3D terrain, GPS tracking, multiple base layers, overlays, and tile caching. Team Sync connects your crew via P2P, LAN, BLE, Reticulum, and drone telemetry — all offline. Built for hikers, hunters, field crews, and search & rescue.

Purchase on Gumroad Google Play Microsoft Store Web Version Support development
100%Offline
3DTerrain
4Platforms
5Sync Modes
Trailhead
Camp
Summit
Water
Waypoint
9,342 ft Elevation
GPS Active
Topo
Sat
3D
3D
+
−
0.5 mi
39°05'N 108°34'W
OpenTopo Satellite 3D Terrain Contours BLM
01

Built for the backcountry

ZYRN TOPO is for anyone who needs reliable maps beyond cell coverage. Honest, capable, offline-first mapping tools.

Hiking & Backpacking

Plan routes, track progress, mark camps and summits. Topo, satellite, and 3D terrain layers with full offline support and auto tile caching.

Hunting & Fishing

Mark stands, blinds, water sources, and access points. BLM public lands and USFS Motor Vehicle Use Map overlays built in.

Field & Survey Work

GPS tracking, coordinate formats (DD, DMS, DDM, UTM, MGRS), point elevation data, and offline operation for remote sites.

Search & Rescue

Assign operational periods, draw lines and polygons, record tracks, and coordinate teams in real time via P2P, LAN, or radio — all without a signal.

02

Everything you need in the field

Offline maps, 3D terrain, GPS tracking, markers, lines, polygons, real-time Team Sync across 5 transports, and full data management — all in one app, all offline.

5 Base Layers

  • OpenStreetMap — worldwide street map
  • OpenTopoMap — topographic contours
  • Esri Satellite — high-res aerial imagery
  • CartoDB Voyager — clean terrain view
  • CartoDB Dark Matter — dark theme

3D Terrain View

  • MapLibre GL JS WebGL rendering
  • Real DEM elevation data (Mapterhorn)
  • Drapes any base layer over 3D mesh
  • Hillshade + sky atmosphere
  • Pitch, rotation, and zoom controls

5 Overlays

  • Contour lines (OpenTopoMap)
  • Hillshade relief shading
  • OpenSnowMap slope angle
  • BLM Public Lands boundaries
  • USFS Motor Vehicle Use Maps

Shaded Relief

  • Normal, Enhanced, and Terrain modes
  • Adjustable overlay opacity
  • Per-overlay opacity control
  • CalTopo-style layer management
  • Night mode toggle

Custom Sources

  • Add WMS / WMTS tile services
  • Add WFS vector feature services
  • Custom layer name & URL
  • Live preview in layer panel
  • Persisted across sessions

Map Controls

  • Compass rose with heading-up mode
  • Map rotation support (leaflet-rotate)
  • Center crosshair for precision
  • Coordinate display (5 formats)
  • Context menu on long-press

Markers & Waypoints

  • Drop markers at any location or GPS
  • Custom name, notes, and color
  • 50+ pin icon types
  • Tap marker for info/edit/navigate
  • Photo waypoints from camera

Lines & Polygons

  • Draw lines on map with tap or freehand
  • Draw polygon areas
  • Custom color per object
  • Buffer zones and range rings
  • Sector/wedge drawing

Folders & Organization

  • Create folders to group objects
  • Assign objects to folders
  • Toggle folder visibility on map
  • Search and filter map items
  • Object context menu (edit/delete/move)

Operational Periods

  • SAR-style operational period management
  • Custom name, color, and thickness
  • Toggle period visibility
  • Assign objects to periods
  • Period-based filtering

Team Members

  • Add team members with roles
  • Contact info and status
  • Import/export team as CSV or JSON
  • Team management panel
  • Assign members to operations

Gear / Pack List

  • Full gear inventory management
  • Weight tracking per item
  • Category organization
  • Import/export gear as CSV or JSON
  • Pack weight summary

GPS Location

  • Real-time GPS with live position
  • 3-state center: off → follow → heading-up
  • GPS accuracy circle on map
  • Drop marker at current GPS
  • Navigate to any point

Track Recording

  • Start / stop track recording
  • Live distance, time, and speed
  • Track polyline drawn on map
  • Save recorded tracks as objects
  • Track bar with live stats

Measure Tools

  • Point-to-point distance measurement
  • Area measurement for polygons
  • Bearing / heading between points
  • Elevation profile along path
  • Live measurement display

Navigation

  • Navigate to any marker or search result
  • Bearing and distance to target
  • Navigation bar with live updates
  • Stop navigation button
  • Works fully offline

Search

  • Nominatim geocoding search
  • Search by place name or coordinates
  • Jump to any location on map
  • Search results as markers
  • Coordinate paste support

Point Info

  • Tap anywhere for elevation data
  • Coordinates in DD, DMS, DDM, UTM, MGRS
  • Weather data from NWS forecast
  • Point info floating panel
  • Copy coordinates to clipboard

Drawing Tools

  • Lines, polygons, and freehand drawing
  • Buffer zones around objects
  • Range rings (concentric circles)
  • Sector/wedge shapes
  • Drawing status pill with undo

Color Picker

  • Full color picker for every object
  • Preset color grid
  • Applied to markers, lines, polygons
  • Color persistence across saves
  • Visual color preview

Print to PDF

  • Print current map view as PDF
  • Includes all visible objects
  • High-resolution output
  • Landscape and portrait options
  • Map title on printout

Night Mode

  • 3-state cycle: off → dim → dark
  • CSS filter-based map dimming
  • Preserves UI readability
  • Quick toggle from layers panel
  • Separate from base layer choice

Settings

  • Coordinate format selection (5 types)
  • Default base layer choice
  • GPS accuracy preferences
  • Unit system selection
  • Permission management

Weather

  • NWS forecast for any US location
  • Temperature, wind, conditions
  • Forecast period display
  • Accessed via point info panel
  • Works at any tapped coordinate

Offline-First Architecture

  • Service Worker stale-while-revalidate
  • All data stored locally (localForage)
  • Works from first offline visit
  • Graceful offline placeholder tiles
  • Offline mode banner

Auto Tile Caching

  • Every tile viewed is cached automatically
  • Background caching via Cache API
  • no-cors fetch for all tile servers
  • Deterministic subdomain for cache keys
  • 7-day background refresh

Bulk Tile Download

  • Download current layer for viewport
  • Download ALL layers for viewport
  • Zoom ±2 levels pre-cached
  • Progress bar with cancel
  • Confirmation for large downloads

Cache Management

  • View cached tile storage size
  • Clear tile cache button
  • Clear app cache separately
  • Storage used display
  • Map objects unaffected by cache clear

3D Terrain Offline

  • DEM tiles cached by service worker
  • Mapterhorn tiles in TILE_HOSTS
  • Hillshade cached for offline use
  • 3D view works in cached areas
  • Terrain exaggeration preserved

Data Security

  • All data stays on your device
  • No telemetry or analytics
  • No account required
  • Export/import for backup
  • Your data, your device

Export

  • GeoJSON with CalTopo simplestyle (round-trip)
  • GPX 1.1 with gpx_style colors (Gaia, Garmin)
  • KML / KMZ for Google Earth
  • CSV for spreadsheets
  • Print to PDF

Import

  • GeoJSON import with merge
  • KML/KMZ file import
  • GPX track and waypoint import
  • CSV data import
  • Drag-and-drop support

Persistence

  • Auto-save to localForage (IndexedDB)
  • Map title saved with data
  • Settings saved separately
  • Survives app close and restart
  • Multiple save slots via export

Gear Import/Export

  • Export gear list as JSON
  • Export gear list as CSV
  • Import gear from file
  • Weight and category preserved
  • Bulk gear management

Team Import/Export

  • Export team roster as JSON
  • Export team roster as CSV
  • Import team from file
  • Roles and contact info preserved
  • Share team configs

Local Storage

  • IndexedDB via localForage
  • Cache API for map tiles
  • No cloud dependency
  • Works fully air-gapped
  • Persistent across updates

P2P Mesh (Trystero)

  • WebRTC peer-to-peer via Nostr relay
  • No server required — share a session code
  • Live peer location circles on map
  • Encrypted, end-to-end data channel
  • Team chat + map object sharing

LAN Hub (relay.mjs)

  • Node.js WebSocket relay server
  • All devices connect to one LAN IP
  • Works with zero internet access
  • QR code for easy device onboarding
  • Includes built-in ATAK CoT bridge

Bluetooth LE

  • Direct device-to-device via BLE
  • No WiFi or internet required
  • Peripheral and central roles
  • Location and text message exchange
  • Android powered by Capacitor BLE

Reticulum & LXMF

  • Long-range mesh — LoRa, serial, or TCP
  • Add devices by 32-hex LXMF address
  • Sideband-compatible (announce + messaging)
  • Persistent identity across restarts
  • Auto-spawning bridge on Linux desktop

Drone Telemetry (MAVLink)

  • MAVLink v1/v2 binary parsing
  • Live drone position on map
  • Battery, flight mode, and altitude
  • HEARTBEAT, SYS_STATUS, GPS_INT
  • Connect via WebSocket or TCP bridge

ATAK / soRD CoT

  • Bidirectional CoT — your team appears on ATAK
  • UDP multicast 239.2.3.1:6969, type a-f-G-U-C-I
  • Stale-time auto-removes offline peers
  • soRD detections — red ≥85% / orange 60–85%
  • Python bridge bundled & auto-spawned
03

Base Layers & Overlays

Switch between base maps and overlays instantly. All layers are cached automatically for offline use.

OpenStreetMap
Base
OpenStreetMap
OpenTopoMap
Base
OpenTopoMap
Satellite
Base
Esri Satellite
Voyager
Base
CartoDB Voyager
Dark
Base
CartoDB Dark
Contours
Overlay
Contour Lines
Hillshade
Overlay
Hillshade
Slope
Overlay
Slope Angle
BLM
Overlay
BLM Public Lands
MVUM
Overlay
USFS MVUM
USGS Topo
Overlay
USGS Topo
04

Every platform, one app

Deploy the same full-featured app on every device you carry into the field. No platform-specific limitations.

Android

Google Play, APK / AAB
Min Android 7 (API 24)

Windows

NSIS installer, portable EXE, ZIP
Min Windows 10

Linux

.deb / .tar.gz
Mesh bridges auto-spawn

Web

Any modern browser
PWA installable

Ready for the field?

One purchase. No subscription. No account required. Full-featured on Android, Windows, Linux, and web — with or without a signal.

Hikers, hunters, field crews, search & rescue — wherever the map ends.

Purchase on Gumroad Google Play Microsoft Store Web Version Support development