https://link.springer.com/content/pdf/10.1007%2F978-1-4614-8579-7_8.pdf ///  Chapter 8    Data Analysis on Location-Based Social Networks 

1.Typical online location-based social networking sites provide location-based services that allow users to “check in” at physical places, and automatically include the location into their posts. “Check-in” is an online activity that posts a user’s current geographical location to tell his friends when and where he is through social media. 

2.Compared with many other online activities (following, grouping, voting, tagging,etc.) that interact with the virtual world, “check-in” reflects a user’s geographical action in the real world, residing where the online world and real world intersect.

3. The information layout of location-based social networks.

The geographical layer contains the historical check-ins of users, while the social layer contains social friendship information, and the content layer consists of user feedbacks or tips about different places. All these three layers share one timeline, indicating the temporal information of the user “check-in” behavior.