Small differences between manual and automatic formants measurements

Question

After the implementing of the Praat script where formants was measured automatically, I found an small differences between manual and automatically measured formants. Who knows, why this differences are existing? See more information below:

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Praat Script:

start = 0.445
end = 0.49949542580791223
vowel_duration = end - start
vowel_mid_time = end - (vowel_duration/2)



### formants for  mid time
Move cursor to: vowel_mid_time
f1_vowel_mid_time$ = Get first formant
f2_vowel_mid_time$ = Get second formant
f3_vowel_mid_time$ = Get third formant



### formants for  end time
Move cursor to: end
f1_vowel_end_time$ = Get first formant
f2_vowel_end_time$ = Get second formant
f3_vowel_end_time$ = Get third formant

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Time point:
start time of the vowel: 0.445
mid_time of the vowel: 0.4722477129039561
end_time of the vowel: 0.49949542580791223

Automatic measurament:

f1_mid = 611.2670572939114 Hz (nearest F1 to CURSOR)
f1_end = 347.9625660876839 Hz (nearest F1 to CURSOR

f2_mid = 1456.6771398810374 Hz (nearest F2 to CURSOR)
f2_end = 1386.7518424074453 Hz (nearest F2 to CURSOR)

f3_mid = 2466.7302196075952 Hz (nearest F3 to CURSOR)
f3_end = 2512.137349760532 Hz (nearest F3 to CURSOR)

Manual Measurament:

f1_mid = 610.4667330034513 Hz (nearest F1 to CURSOR)
f1_end = 298.4994941061535 Hz (nearest F1 to CURSOR)

f2_mid = 1456.512849969646 Hz (nearest F2 to CURSOR)
f2_end = 1394.1468860327666 Hz (nearest F2 to CURSOR)

f3_mid = 2467.4351107904986 Hz (nearest F3 to CURSOR)
f3_end = 2536.6386804839294 Hz (nearest F3 to CURSOR)

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