Trail Signal is a UK-based mapping application that shows mobile phone signal coverage on hiking and walking routes. It is provided by Usefulish Ltd, a company registered in England and Wales.
Data Controller: Usefulish Ltd (company number 17360947)
Registered office: 71-75 Shelton Street, Covent Garden, London, WC2H 9JQ
Contact: admin@usefulish.uk
For the purposes of UK GDPR, Usefulish Ltd is the data controller for the personal data described in this policy.
When you sign in, we receive basic information from your authentication provider (Google Sign-In via Firebase Authentication):
We do not store your password. Authentication is handled entirely by Google/Firebase.
When you use the Record Walk feature on the mobile app, we collect GPS coordinates from your device at regular intervals (approximately every 3 metres of movement). This data includes:
GPS data is collected only while you are actively recording a walk. We do not track your location in the background at any other time. You start and stop recording manually.
If you enable Background Location permission, GPS recording continues when the screen is off or the app is in the background — but only during an active recording session that you have started.
During recording, the app collects information about the mobile cell tower your phone is connected to. This includes:
This data is paired with your GPS location to build a picture of where signal coverage exists along your route.
When you upload a GPX file (a standard GPS route file), it is stored privately in your account. GPX files contain GPS waypoints and track points that describe a hiking route.
After recording a walk, cell signal observations from your track are contributed to the Community Signal layer — but only if you have enabled Community Signal sharing, which is off by default. They are anonymised before upload. This shared dataset helps all users see where signal coverage exists. See Section 5 for details on how this data is anonymised.
If you choose to share a walk live, your current position and route so far are sent to our server and shown to anyone who has your private share link (and, if you set one, its PIN). This only happens while a share you started is active. You can stop sharing at any time in the app; sharing ends automatically when the recording stops, and the shared data is deleted from the server within 24 hours of the walk ending (48 hours at the latest). Live sharing shows your precise location by design, including near any Privacy Zone.
| Data | Purpose | Lawful Basis |
|---|---|---|
| Account data | Identify you and sync your data across devices | Contract (providing the service) |
| GPS tracks | Record your walking route for personal review | Consent (you choose to record) |
| Cell signal data | Map signal coverage along your route | Consent (you choose to record) |
| GPX uploads | Store your planned routes for use in the app | Contract (providing the service) |
| Community Signal | Improve coverage data for all users | Consent (sharing is off by default; you enable it in Settings → Privacy → Community Signal, and can turn it off at any time) |
Your account data, GPX files, and recorded tracks are stored in:
User data is stored in a private storage bucket that has no public URL. It can only be accessed through our authenticated API, which verifies your identity before returning any data. No one else can access your routes or tracks.
The mobile app stores data locally on your device using IndexedDB (a browser/app storage mechanism):
This data stays on your device and is not transmitted unless you choose to sync it.
Cloud data is stored on Cloudflare's global network and Google's Firebase infrastructure. Both providers maintain appropriate safeguards for data stored outside the UK, including standard contractual clauses where applicable.
When your recorded walk data is contributed to the Community Signal layer:
Community Signal data is stored publicly and is accessible to all app users as part of the coverage map.
You can set a privacy zone (for example around your home) so that readings inside it are excluded from what you contribute to the public map.
Please note: the privacy zone only sanitises the anonymous crowdsource upload. It does not remove coordinates from your own recorded tracks, routes, or GPX files stored in your account — these keep their full coordinates so you can review them, including any points that start or end near your home. Only you, via your login, can access them.
We do not sell your data. We share personal data (including, where noted, your IP address) only with the processors below, each of which acts on our behalf and maintains its own privacy policy and data processing terms:
Map fonts and tiles are self-hosted. Map glyphs/fonts and the map tiles are served from our own Cloudflare storage (tiles.trailsignal.uk), so no third-party map-font provider receives your requests. In the rare case that our primary map style fails to load, the app falls back to the public MapLibre demo tiles (demotiles.maplibre.org), which would then receive your IP address; this is an edge case only.
We do not share your personal data with advertisers, analytics companies, or any other third parties.
| Data | Retention |
|---|---|
| Account data | Until you delete your account or request erasure |
| GPX routes | Until you delete them or delete your account |
| Recorded tracks | Until you delete them or delete your account |
| Community Signal contributions | Retained indefinitely as aggregate map data; when you delete your account we erase the identifier linking contributions to you, after which they are anonymous |
| On-device data | Until you clear app data or uninstall the app |
We keep your routes and tracks until you delete them or delete your account; we may delete data belonging to accounts that have been inactive for 24 months.
You can permanently delete your whole account and all its data yourself at any time — in the app (Settings → Account → Delete account) or on the web (account panel → Delete account). See how to delete your account. You can also request deletion by emailing admin@usefulish.uk.
Under UK GDPR, you have the following rights:
To exercise any of these rights, contact us at admin@usefulish.uk.
You also have the right to lodge a complaint with the Information Commissioner's Office (ICO):
ico.org.uk/make-a-complaint | Helpline: 0303 123 1113
You must be at least 16 to use Trail Signal. Trail Signal is a general-purpose walking tool and is not directed at children, and we do not knowingly collect or process personal data from anyone under 16. If you believe someone under 16 has provided us with personal data, please contact us and we will delete it.
Trail Signal does not use tracking cookies or advertising cookies. We use browser localStorage and IndexedDB solely to store your app preferences (map position, layer settings) and offline data. No data is shared with third-party analytics or advertising services.
We may update this policy from time to time. Material changes will be communicated through the app. The "last updated" date at the top of this page will always reflect the current version.
If you have questions about this privacy policy or how we handle your data:
Usefulish Ltd (company number 17360947)
71-75 Shelton Street, Covent Garden, London, WC2H 9JQ
Email: admin@usefulish.uk