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How do you retrieve the values of the frequency component occurring in a 2D freq spectrum?

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I have this, and if I wanted to know the values of the white dots. what should i do ?

I apolgize beforehand for asking this question.

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You have a signal in a 2D-frequency domain. You know the maximum frequencies in both directions, I assume. Hence, you know which bandwidth is represented by one pixel and then... just count the pixels from the center to the point of interest along the axes and your done. Depending on your application, taking the Euclidean distance from the center to the peak is also an option, which does end in one instead of two frequencies.

If you would like to do a more sophisticated approach, you could fit a Gaussian distribution (or another function, if you have one in mind that is more appropriate in your case) to the peak. That way you could get a sub-pixel accuracy of the location of the peak.

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In the following paper, there is an implementation of the ML estimator for this problem:

Selva, J., "Efficient maximum likelihood estimation of a 2-D complex sinusoidal based on barycentric interpolation," in Acoustics, Speech and Signal Processing (ICASSP), 2011 IEEE International Conference on , vol., no., pp.4212-4215, 22-27 May 2011 doi: 10.1109/ICASSP.2011.5947282 URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5947282&isnumber=5946226

Also, there is one implementation for the 1-D case in

http://www.dsprelated.com/showcode/164.php

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