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#8821
Rasa Bhattarai
Participant

Hello @grant,

Thank you for allowing me to ask queries regarding eye tracking. I came across one third party open source software which is used for analyzing post eye tracking points. I ran it’s sample program (along with the data points that it provided) and it was regarding fixation_detection. I want to learn how do these fixation points give out saccade amplitude and velocity (Similar to these graphs? The values that is obtained in the output of the program is as such:

Fixations:
Total Number of Fixations(t1,t2,minDur): 22
Total Number of Fixations(t1,3s,minDur): 22

t1,t2,minDur:
ID-Xcenter-Ycenter-Nt1-Nt2-StartTime-EndTime-Duration
1 689.5723 363.6341 70 70 1000.3780 3350.5640 2350.1860
2 1037.1145 367.1904 27 27 3451.1380 4350.4660 899.3280
3 684.5436 716.0460 28 28 4450.2700 5381.6600 931.3900
4 326.7230 361.5158 27 27 5481.6370 6348.1720 866.5350
5 680.4622 -2.4757 30 29 6448.7920 7414.7770 965.9850
6 680.0611 357.9217 28 28 7514.9370 8414.8190 899.8820
7 1026.4849 360.3656 29 28 8548.6230 9448.3750 899.7520
8 674.2867 714.6757 28 27 9548.4600 10415.1300 866.6700
9 326.8549 355.5990 28 28 10514.6500 11414.0100 899.3600
10 627.2755 26.5071 7 7 11481.5300 11680.9700 199.4400
11 665.6554 13.0811 24 24 11714.7600 12481.1100 766.3500
12 681.1126 362.2682 30 30 12573.5100 13514.4300 940.9200
13 667.8339 13.6558 30 28 13580.7600 14547.6200 966.8600
14 684.5231 719.7679 30 30 14613.8500 15580.9300 967.0800
15 319.6370 359.0985 29 29 15647.5700 16580.6700 933.1000
16 1036.1421 360.5191 26 26 16747.2700 17580.6900 833.4200
17 672.2159 354.2256 29 29 17647.3300 18580.8400 933.5100
18 1034.1954 348.7120 30 30 18647.3000 19613.7400 966.4400
19 689.1827 713.7524 29 28 19746.9800 20647.1400 900.1600
20 327.0446 345.6037 28 28 20747.3200 21647.1000 899.7800
21 682.1914 -8.3242 29 29 21747.4100 22680.6700 933.2600
22 689.3789 364.1872 9 9 22747.5300 23014.5400 267.0100

These x and y center shows the fixation centers in pixels/screen coordinates. I tried using the method you said to calculate saccade velocity. But I do not understand how is it that researchers use degree/second to calculate it ? I mean the value that is given here is shown in pixels. So how do I convert it to degrees/second to calculate saccade velocity ?

I am sorry if it is too much to ask. I did not get reply from other sources.

Thank you