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FAQ: How do the EyeLink system and Data Viewer calculate degrees of visual angle?
Sam
Research Support Specialist
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Joined: Aug 2020
Posts: 999

#1
09-04-2020, 04:01 PM
The EyeLink system and Data Viewer calculate visual angles using the viewing distance (screen_distance) and screen dimension (screen_phys_coords) values specified in the PHYSICAL.INI file on the EyeLink 1000 and EyeLink II, or the Screen Settings page in the tracker Configuration Manager on the EyeLink 1000 Plus or EyeLink Portable Duo. It is important that these values are correctly specified, or else the calculations of visual angle and velocity will be inaccurate.

For detailed instructions on how to set these parameters, please see this post or the appropriate installation guide for the specific EyeLink system:
* For further information on visual angle, please see our blog post on this topic.