What is JTrack?¶

A Collaborative Tool for Passive Monitoring and Ecological Momentary Assessments

Scope of Application¶

The JTrack platform consists of a web dashboard (JDash) and two mobile JTrack applications (EMA and Social). We also provide server infrastructure to enable central data collection with JTrack.

The platform was developed to gather study-specific digital phenotyping information like various sensor data and participants’ (i.e., “users”) self-perceptions of specific events or activities occurring in their daily lives.

JTrack was designed as an open-source collaboration tool to enable clinical and behavioral researchers to collect their own digital phenotyping data from study populations.

The JTrack Social application was developed to collect sensor data from sensors embedded in modern smartphones and smartwatches, as well as general smartphone usage information. The specific sensor and phone usage combinations are study-specific and fully customizable.

A high priority is assigned to data privacy to ensure that the collected data does not contain any identifiable or personal information. For example, GPS information is encoded into a random coordinate system to ensure that the user’s actual location cannot be derived.

JTrack Social has two different modes that can be used selectively or in combination:

Passive monitoring: records data in the background with only a minimal interaction by the user.
Active labeling: the user enters a specific activity they are performing and recorded sensor data is labeled accordingly.

The JTrack EMA application was developed to collect questionnaire data in longitudinal studies. Using JTrack EMA, one can collect “user-generated” data based on users’ interactions or responses to customizable surveys. This data is collected, transferred, and stored on our servers anonymously.

Additionally, both apps may collect “derivative data”, which is gathered automatically for technical purposes — such as sending push notifications, logging errors, or maintaining smooth app performance. This data is not stored permanently and does not include any user-identifying information.

Both apps only collect data from users who have registered for a study and accepted the necessary permissions provided during installation. Installing the applications without participating in a study will not result in any data collection or storage. For all participants, only study-specific information is collected, as specified in the written informed consent.

Sensor Data¶

The following is a non-exhaustive list of data that can be collected using the JTrack Social platform:

2.1 Location Data¶

Relative GPS locations are recorded, providing the phone’s position relative to an anonymized reference point. This tracking allows estimation of mobility (e.g., distance covered per day) and the number of unique locations visited.

Anonymization: All location data are anonymized using a random reference point with rotation, ensuring that the actual location cannot be identified.

2.2 Smartphone Usage¶

The number, timestamps, and duration of phone calls can be recorded, along with the number of incoming and outgoing messages. This provides estimates of phone use for social communication.

Anonymization: No sensitive information (e.g., phone numbers, recipients, or message contents) is recorded.

2.3 Activity Recognition¶

The time and duration of the following activities can be collected automatically: in vehicle, on bicycle, running, walking, still, phone tilting.

Anonymization: Activity recognition is performed on the device, and only the time and type of recognized activities (associated with an anonymized device ID) are collected.

2.4 App Usage¶

Timing, duration, and app names can be collected to evaluate social vs. non-social smartphone usage (e.g., gaming, social communication, internet browsing).

Anonymization: Only app names and timestamps are collected—never the content of user interactions.

2.5 Accelerometer and Gyroscope¶

Accelerometer and gyroscope data can be recorded to estimate movement patterns.

Anonymization: These data are only combined with anonymized, JTrack-specific study and subject IDs.

Sample Data¶

Curious about how this data would look like? Contact us to get a sample dataset.

Ecological Momentary Assessments¶

Information collected in each study is outlined in the written informed consent and study protocol. Such information may include:

3.1 User-Generated Survey Data¶

Information provided by users when completing surveys is stored separately from any personal data. All survey responses are confidential and not used to identify participants.

Demographic and clinical data may be collected if specified by the study protocol. Access to this information is restricted to authorized study personnel only.

3.2 Derivative Data¶

Data automatically collected by the application (e.g., app version, device operating system, log files) are temporarily stored and deleted when the application is uninstalled. No employee has direct access to this data, and it cannot be linked to identify any person.

Application Permissions¶

Our apps may request access or permission to certain device features. These features are necessary to provide a smooth experience and to access study-specific sensors.

Below is a list of permissions the application may request:

Camera access: Used to scan QR codes for app activation.
Location information: Required for location tracking. Coordinates are anonymized on the device before transfer to the server.
File read and write access: Used to write and save survey information (e.g., images).
Battery optimization: To prevent the application from being put to sleep, we ask users to disable the system’s battery optimization.

Users can modify permissions at any time via the device settings.

4.1 Push Notifications¶

If required, we may request permission to send push notifications. Notifications can be:

Online notifications, sent by our servers to deliver information.
Offline notifications, generated by the app to inform users about new questions or operational status.

Data Usage¶

5.1 Intended Use of Collected Information¶

We may use information collected via JTrack applications to:

Conduct data analysis for internal purposes and publication (e.g., journals, conferences) as specified in study protocols.
Share anonymized data with other researchers (if covered by study protocols and informed consents).
Improve the efficiency and operation of the applications.
Resolve technical issues and troubleshoot problems.

5.3 Disclosure of Information¶

Personal information is never shared with individuals not involved in the study. It will never be used to contact you for reasons unrelated to the study. Data you provide will never be sold or used for marketing or advertising. We may share anonymized data to address scientific questions or verify study results.

Data Security¶

To help secure information, we use administrative, technological, and physical safeguards.

All data transfers are protected via HTTPS. Additional checks (e.g., MD5 checksums) prevent errors and ensure integrity. Unique identifiers (e.g., user and device IDs) are generated randomly.

Any personally identifiable information is stored separately and never linked to user-generated data. All employees with access to study data are contractually obligated to maintain data security.

Study Participants¶

Users may stop data collection or leave the study at any time via the app. If a device is lost, participants may request that study owners stop data collection.

If data collection is not anonymized and a participant leaves the study, they can request deletion of their data—unless the data have already been used in publications, in which case regulations require retention for up to 10 years (or as specified in the protocol).

Data Access¶

Access to collected data is limited to qualified employees or researchers involved in the study. Access to personal information is limited to study personnel responsible for data collection.

All employees are contractually obligated to maintain data security and comply with this policy. They will never attempt to re-identify participants or contact them for purposes beyond the study protocol.