How I can calculate saccade ampłtude in degree, if I have xand y coordinates in pixels.. Which formula, algorithm, software can help.. I have used tobii for data collection.
It is strange that tobii should not provide software doing that conversion, but here is the way to do it:
what is the 'd' value here in formula?
is that 'the distance between participants and screen'?
and what algorihms i should apply on this eye tracking data
You are right about the viewing distance. I mentioned d in the first sentence on the image.
Concerning algorithms, could you clarify your question? What is it that you want to achieve?
Detlef Ruschin thanks alot for your response!
I have fixation point X-Y coordinates in [MCS norm] and [DACS px] form. what is required fixation point [MCS norm] or [DACS px] to calculate euclidean distance between 2-fixations?
I am not sure what the abbreviations MCS and DACS mean, but my guess is you are asking for the proper unit of measurement for distances.
To compute the inverse tangent correctly, you have to use the same units for distances on the screen and distances between observer and screen. Then the units will cancel in the division term.
Therefore, you either must convert the screen pixels to meters, or you must convert the viewing distance to pixels (which would be a rather unusual procedure).
Deepika, I have just updated my simplified formula with the correct one. In practice, you will hardly notice a difference, but it won't hurt to use the right one. Sorry for any inconvenience.
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