3. Location Data
Your privacy is central to how we handle location data.
Before we store anything, we snap the coordinate your device sends onto a K-anonymity grid. Cells are at least 500 metres on a side and grow larger where fewer people live, so a cell is designed to be shared by around a hundred people or more. What we keep is a neighbourhood, not an address. The original coordinate is never written to our database. The grid is calibrated with United States population data; outside the US we fall back to our largest cell size.
Other participants never see your location or your travel time. Each person is shown their own travel time and a rounded upper bound on the group's longest trip, so you can tell whether a spot is fair to everyone without learning where anyone lives.
We do not sell your location data. When you leave a hangout — or the host removes you, or the hangout is called off — your location is deleted from it straight away. Anything still stored is deleted 30 days after you share it, which is also the furthest ahead a hangout can be scheduled.
5. SMS and Text Messaging
Midpoint uses SMS text messaging for two specific purposes:
• Verification (one-time passcodes). When you sign up, sign in, or add a phone number to your account, we send a one-time code to confirm the number belongs to you.
• Peer invitations. When a friend who already has a Midpoint account invites you to join a hangout, or tags you in a moment from a shared hangout, you may receive a single text message identifying that friend by name and linking to the relevant content.
Message frequency. Message frequency varies based on your activity and your friends' activity. You will only receive verification codes when you actively sign in or change your phone number, and peer invitations only when a friend explicitly invites or tags you. Midpoint does not send any marketing, promotional, recurring, or unsolicited SMS.
Message and data rates may apply. Standard carrier message and data rates apply to all SMS messages you send to or receive from Midpoint. Midpoint does not charge for messaging itself; your wireless carrier's plan determines whether you are charged for sending or receiving each message.
Opting out. You can opt out at any time by replying STOP to any Midpoint SMS. We will record your opt-out and stop sending all future SMS to that number — including verification codes, which means you will no longer be able to sign in by phone unless you re-enroll. Reply HELP at any time for assistance.
We do not sell, rent, lease, or share your mobile phone number or your SMS consent with any third party for marketing or promotional purposes. We share phone numbers only with our SMS delivery provider (Twilio Inc.) for the limited purpose of transmitting the messages you request, and as required by law.