Trail Sense

Use your Android phone's sensors to assist with wilderness treks or survival situations. Designed for entirely offline use.

Trail Sense is a tool, and just like any other tool that you bring into the wilderness, it's essential to have backup equipment and skills.

See the User Guide for a guide on how to use Trail Sense (also available in app, just search on the Tools tab for User Guide).

See the Technical Blog / Research

Table of Contents

• Feature Roadmap
• Goals
• Features
• Privacy
• Contributing
• FAQ
• Open Source Credits
• License

Feature Roadmap

This is the 2026 feature roadmap. It's not a guarantee and it may change. Other features may be included based on what I feel like working on.

• Improvements to / additional map layers
• Improvements to the following tools: Offline Maps, Map, Navigation, and Astronomy
• Performance, stability, and codebase cleanup
• Release of the first plugins (map layers / coordinate formats)

Goals

• Trail Sense must not use the Internet in any way, as I want the entire app usable when there is no Internet connection
• Features must provide some benefits to people using the app while hiking, in a survival situation, etc.
• Features should make use of the sensors on a phone rather than relying on stored information such as guides
• Features must be based on peer-reviewed science or be verified against real world data
• Use Cases

Features

• Designed for hiking, backpacking, camping, and geocaching
• Place beacons and navigate to them
• Follow paths
• Retrace your steps with backtrack
• Use a photo as a map
• Plan what to pack
• Be alerted before the sun sets
• Predict the weather
• Use your phone as a flashlight
• And much more!

See the need for a new feature? Post it here!

Privacy

Location information gathered by this application does not leave your device (as a matter of fact, this app doesn't use the Internet at all). The altitude and pressure history for the last 48 hours is stored in local app storage - this is used to determine weather forecasts. The last known location is also stored in app preferences to allow faster load times and support app functionality when the GPS can not be reached. The beacons and paths store their location information in a local SQLite database. All of this information is cleared when you clear the app storage or delete it.

Permissions

Sensitive

• POST_NOTIFICATIONS
  • Allows Trail Sense to display notifications (backtrack, weather, sunset alerts, astronomy events, water boil timer, etc)
  • When denied: Alerts will not be displayed and some services may not function properly depending on your device manufacturer.
• ACCESS_FINE_LOCATION / ACCESS_COARSE_LOCATION
  • Allows Trail Sense to retrieve your location for navigation, weather (sea level calibration), and astronomy.
  • When denied: You will have the ability to mock your location under Settings > Sensors > GPS. On Android 14+, backtrack and weather will be unavailable due to Android OS constraints.
• ACCESS_BACKGROUND_LOCATION
  • Allows Trail Sense to retrieve your location for sunset alerts while in the background. On some devices, this will also improve the reliability of backtrack and weather monitor (though shouldn't be needed on most devices).
  • When denied: If you travel and do not open Trail Sense, but have Sunset and Sunrise Alerts enabled, the times will likely be inaccurate.
• ACTIVITY_RECOGNITION
  • Allows Trail Sense to use your phone's pedometer for distance calculation.
  • When denied: The pedometer will not work.
• CAMERA
  • Allows Trail Sense to use your camera on the sighting compass, clinometer, and for taking photos used by the Cloud Scanner, QR Code Scanner, and Photo maps.
  • When denied: You will not be able to use the sighting compass, camera clinometer, or QR Code Scanner. You will need to pick an existing photo to use for the Cloud Scanner or Photo maps.
• SCHEDULE_EXACT_ALARM
  • Allows Trail Sense to post a notification at an exact time. This is used by the Clock tool (when updating system time) and Sunset and Sunrise Alerts.
  • When denied: The clock and sunset alerts may not be accurate (can be off by several minutes).

Not sensitive (always granted)

• RECEIVE_BOOT_COMPLETED
  • Allows Trail Sense to restart when you reboot your device. This will re-enable backtrack, weather monitor, and several other background services.
• FOREGROUND_SERVICE
  • Allows Trail Sense to start foreground services, such as backtrack and weather monitor.
• FLASHLIGHT
  • Allows Trail Sense to control the phone's flashlight.
• VIBRATE
  • Allows Trail Sense to vibrate the phone. Used for haptic feedback on dials and on the metal detector tool.
• WAKE_LOCK
  • Allows Trail Sense to reliably run services such as backtrack and weather monitor, especially when the frequency is under 15 minutes.

Contributing

See the CONTRIBUTING.md file for details on contributing to Trail Sense.

Copying

You are allowed to create copies of Trail Sense and rebrand to what you see fit. It is under the MIT license.

Please change the following if you are using this as the base for your app:

• App name
• Package name
• Support email
• App icon (optional)

FAQ

The FAQ has moved to the wiki

Open Source Credits

• Thank you to everyone who tried out this app and opened issues, suggested features, provided translations, or tested debug builds for me
• Please see the in app licenses for all open source licenses
• Contributors and translators: https://github.com/kylecorry31/Trail-Sense/graphs/contributors

License

• MIT license
• Survival Guide License