Privacy Policy
Last updated: 19 October 2026
Trail Stamp (行山喇) is operated by TopoMind Limited ("we"). This page explains what data the app uses, who it goes to, how long it is kept and how to delete it.
Without an account
Routes, offline maps, distance-post stamps, check-in photos and your progress stay on your iPhone.
While you hike, the app uses GPS on your iPhone to match you to the trail and stamp posts. Your location is not sent to us.
When you sign in
Account: Sign in with Apple or Google gives us an account ID and, if you choose to share them, your email address and name. Your name is printed on your certificates.
Sync: your hike records (sections, times, distance posts passed, distance, ascent), GPS tracks, avatar and certificates are stored on our server so they follow you to a new phone.
Purchases: the signed receipts the App Store gives the app (product, purchase and expiry dates), used to confirm your AI Guide Pass. We never see your payment details.
AI Guide
Narrations for sections, discoveries and distance posts are recorded in advance and downloaded to your iPhone; playing them sends nothing about you to an AI service.
When you ask the AI, your question, the last few questions and answers, and the hike data needed to answer (such as your location, progress and the weather) are sent to our server and then to an AI service: mainly Gemini on Google Cloud, with Cloudflare Workers AI as a backup. Answers may be read aloud using Google's speech service.
We don't store your questions or answers. We only record how much AI was used (its cost) per day, to keep usage within limits. Under the providers' business terms, this content isn't used to train their models.
Feedback you send about a narration (its type and your note) is stored to improve the content.
Preventing abuse
The app uses Apple App Attest to prove that requests come from the genuine app; we store a key ID and a counter for each installation.
To give the free Day Pass only once per person, we keep a one-way hash of each sign-in identity that has used it, even after the account is deleted. It cannot be turned back into your email or account.
What we don't do
The app has no ads and no third-party analytics or tracking tools. We don't sell data, use it for advertising, or track you across other apps or websites.
Service providers
Cloudflare: server, database, file storage and the backup AI model.
Google Cloud: AI answers and speech.
Apple: Sign in with Apple, in-app purchases and App Attest.
Google: Sign in with Google.
Maps, weather and trail data are downloaded by the app directly from Hong Kong Government open-data services (Lands Department, Hong Kong Observatory, AFCD). Like any website, they see your IP address and which map area is downloaded.
How long we keep data
Account data: until you delete your account.
Sign-ins: expire after six months without use.
Daily AI usage records: one year.
App Attest keys: deleted after six months without use.
Deleting your account
In the app: Me → Account → Delete account. We immediately delete your account, hike records, tracks, avatar and purchase records. Certificates already issued keep their serial numbers so they can still be verified, but your name is removed. Narration feedback is kept but no longer linked to you.
Deleting your account does not cancel a subscription. Cancel it on your iPhone in Settings › Apple ID › Subscriptions.
Children
The app is not directed at children under 13.
Changes
When this policy changes, we will update this page and the date above.