Your phone's always tracking your data, but you don't always have easy access to it. Some applications, like OpenPaths and Moves, allow you to see that information. They run in the background of your phone, making constant logs of your movements. The more frequent those logs, the better (or "higher-resolution") the data will be.
This was the only group whose data were tracked by Moves instead of OpenPaths. Because Moves has more sophisticated techniques for gathering data, the location data for this group is the most detailed. You can tell this by comparing the paths on this map with those on all of the other maps (the other maps have mainly straight lines, indicating longer gaps in between when their phones were recording logs).
The application Moves, which was used to gather data for this map, is owned by Facebook. If you're already on Facebook, using it means giving up even more your data to a large company.
The family members whose data is depicted had already installed Moves on their phones before the project began. For the rest of us, their story typifies the difficult truth of trying to track your own data: most of the companies who make it easy for you to see your data are also quietly benefitting and making profits off of that same data.
Note how the Mother's mobility is restricted compared to the Grandmother, who often goes on walks around the park, and the Father, who travels frequently around the area.
For this group, I also collected the Father's Facebook data. Though that data isn't represented on this map, it made it easy to determine exactly what day the child was born. On the Father's Facebook wall, there was one day where there was a spike of activity in the form of likes and comments. You can guess just what day in March that was.