Database Lab

Code (Finding ghosts): GitHub
한국어 문서/Korean

We have been studying differences of daily activity between disable people and non-disable. So, we had to gather people's move day by day. We needed a GPS tracker that is stable enough to get 30-100 people's location at once, and easy to install for participants. We've been through a few things, that is another story.
Anyway, we adopted Traccar as our GPS tracking platform base, and we'd already tried several experiments. It worked well, but we got a bad news recently.

GPS is only available outdoors. Today, GPS tracking system are usually built in vehicles such as airplane, ships, trucks, and taxis. They move most of the time except for a few minutes on a shaded path such as a tunnel. So, it's easy to get the location data from these objects. There are not too many tracking devices that also fit perfectly by types of vehicle. Well then. How about the location of people? Can we still get data from individual person through GPS Tracker like Traccar?

Today's people mostly spend their time inside: home, office, subway, shopping mall and so on. GPS cannot get indoor position so that we can just see where people move from a place to another place. What's more, if people send their location data through small devices like smartphone, we will face numerous smartphones. Unlike the devices for vehicles, there are a lot of things varied such as its OS, the version of OS, manufacturer, hardware conditions, etc.
So, we got some potential issues:

• Most of data doesn't show precise position. It is an estimated value of its place.
• The tracker device are so varied. It is so hard to comprehend.

Besides, it is sufficient so that we can get the places our participant visits, although we don't catch actual location where they are in each place.

While we believe we know the testers' stay points, Dr. Jun, our fellow researcher, reported some clients didn't send data for several hours. It could be problem.

1. If any movement was existed in the gap, the data for many hours have been lost.
2. If not, it is fine. Nothing to do.

We must look into which is right.

Unfortunately, we don't have the specific information of previous participant's devices. So, we should imagine the device which might cause some problems and should be sifted out before experiment begin. First, we picked old phones with some troubles. We want to know whether these legacy devices can run Traccar client properly. Because no small number of our study targets is the disabled and the aged. Some of them use a quite old phone that might have hardware or software issues.¹⁾

Test starts: 20190121

Both devices have sent location data for a week. To get more information, go to the GitHub link above.

We configured the client to send its location every 60 seconds. Theoretically, it should've transmit data within 1-2 minutes even if there is some include calculation delays. Here is count of the gaps in minute.

Overall The result in detail is written in GitHub above.