It sounds like you know how to get to the invite code from a card, but I'll still include some of those steps in case it helps others.
This is how to get the user's list of cards.
Doc: https://developer.glympse.com/docs/core/api/reference/cards/get
Endpoint: https://api.glympse.com/v2/cards
This is how to get the details about a single card. You can also optionally pass "members=true" and/or "invites=true" to this call to get added details.
Doc: https://developer.glympse.com/docs/core/api/reference/cards/id/get
Endpoint: https://api.glympse.com/v2/cards/{cardId}?members=true
This is how to get a member of a card. The last ticket that was shared to the card will be found in the member's invite_code value.
Doc: https://developer.glympse.com/docs/core/api/reference/cards/id/members/mid/get
Endpoint: https://api.glympse.com/v2/cards/{cardId}/members/{memberId}
This is how to get the location data associated with a ticket invite code.
Endpoint: https://api.glympse.com/v2/invites/{inviteCode}?next={x}
The 'next' value is used to get just the location updates since the last call. When first querying an invite code, 'next' should be set to 0. For future calls on the same invite code, you should pass the 'next' value found in the previous call's result.
The location data is returned as a JSON array of delta values. More info on delta encoding here...
Doc: https://developer.glympse.com/docs/core/api/reference/tickets/id/append_location/post