emTripLog is a generalization of the emission platform intended to be used by other researchers to conduct studies on human travel data. On first install, the app does not collect or transmit data. Once the user clicks the link or scans the QR code to join a study, she is asked to consent to the data collection and storage, and then the app begins functioning as desired.
At its core, the app represents an automatically sensed travel diary, constructed from background sensed location and accelerometer data.
Continued use of GPS running in the background can dramatically decrease battery life.
Therefore, we automatically turn the GPS off if you are not moving. This reduces the battery drain caused by location tracking significantly - our tests show that this app results in 10 - 20% additional drain over 24 hours.
If this is still unacceptably high, you can switch to medium accuracy tracking, which should result in ~ 5% additional drain.
For more details on the power/accuracy tradeoff, please see our Technical Report.
https://www2.eecs.berkeley.edu/Pubs/TechRpts/2016/EECS-2016-119.pdf
Other researchers can use this diary according to the behavior they wish to study. For example, if they are interested purely in observing behavior, they can display only the diary. If they are interested in modifying behavior, they can display data gleaned from the behavior. If they are interested in perceptions, they can allow users to provide contextual data about trips in the diary. For more details, see our TRB paper:
https://people.eecs.berkeley.edu/~shankari/emission_trb_2017_paper.pdf