Co-registration refers to the simultaneous recording of multiple data streams. Co-registration of eye tracking data and other data streams helps, in some experiments, to get a better understanding of human behavior. The most common data streams that are recorded simultaneously with eye tracking are EEG, biometric measures such as GSR, ECG or EMG, and motion capture measures.
There are two main points to consider when we want to co-register eye tracking with another data stream - the recording setup and the analysis of the data streams. During the recording phase, it is important that the co-registration solution ensures that the data streams will be synchronized in time. During the analysis, it is also important that the co-registration solution allows you to run the type of analysis and get the metrics that you need to answer your research question. Thinking about these two points before starting your experiment will help you choose the best co-registration solution for your needs.
Tobii Pro divides the solutions for co-registration of eye tracking and other measures into two main categories:
Integrated recording and analysis: with this type of solution, all the data streams are recorded and analyzed in one software program. Integration solutions are most suitable for users who want to record and visualize their synchronized data streams together and run basic analysis.
Synchronized recording: this type of solution ensures that the data streams will be synchronized based on common events sent during the recording. Synchronized solutions are the most flexible ones and are compatible with many external devices and manufacturers.
Combined analysis: This type of solution will also ensure that the data streams will be synchronized for later analysis. In addition, the solution will offer advanced analysis tools for all your data streams and includes a software program that will merge raw and processed eye tracking with the other data streams for combined analysis.
The available solutions for co-registration of Tobii Pro eye tracking data with other data streams will be mainly determined by the eye tracking recording software that is used. In the following tables, you can find an overview of the available Tobii Pro solutions for co-registration of screen-based and wearable eye trackers with other devices.
 – Tobii Pro Lab sends accurate TTL events at the onset of every stimulus to any external device with a TTL input port.
 – StimTracker (Cedrus®) is a hardware device that sends accurate TTL common events to the eye tracking and external data based on a light sensor attached to the stimulus monitor.
 – Tobii Pro Glasses 2 and 3 can send 1-bit LVTTL events to any external device compatible with LVTTL (3V). They are also capable of receiving 1-bit TTL events during the recording (max. 5V). The events can be used to timestamp important events during the recording or to synchronize Tobii Pro Glasses 2 and 3 with other data streams.
 – Tobii Pro Glasses 2 and 3 can receive TCP/IP events using their API. The events can be used to timestamp important events during the recording or to synchronize Tobii Pro Glasses 2 and 3 with other data streams.
 – Tobii Pro Glasses 2 and 3 clocks can be synchronized with an NTP server. All the external devices that share the same NTP clock can be automatically synchronized based on the recording start timestamp with one-second precision.
 – Solution compatible with Tobii Pro screen-based eye trackers and Tobii Pro Glasses 2.
 – Solution compatible with Tobii Pro screen-based eye trackers.