Query regarding the correlation quality in PIVLAB

[Shivani Jariwala]

Hello William,

First of all thank you very much for developing PIVLAB software,  it works great with my data. I am trying to obtain SNR (Signal to noise ratio) for which I am plotting the Cross-correlation matrix and visually seeing if the primary peak is prominent enough than the noise. 

However, when I am processing the images using "Normal" Correlation quality I am able to see the noise around the peak in the correlation matrix. But, when using the "Extreme" correlation quality function to process the same data somehow the entire noise does not show up. I am not able to understand why this happens. The figures are attached with this email. Can you please give some information about the reason and logic behind this, please?

Your help will be much appreciated.

Thanks

Shivani

[William Thielicke]

Hi Shivani,

good obervation! "Extreme" quality enables repeated correlation (a paper on this has just been submitted). The purpose is reducing noise (which apparently works pretty well), by multiplying correlation matrices. 

What data format does the correlation matrix have? Is it double or uint8?

If it is uint8, then you can't see the noise, it is clipped off. But if it is double, you will see it. Maybe try a log z-axi scaling to show also low numbers.

[Fu Fa]

Hi,

How do can I make plots of Signal to noise ratio, obtain signal to noise ratio? and plots similar to the ones above?

[hakeem.b...@gmail.com]

Shivani, 

Hello. What program did you use for the two images attached? I am looking for new programs for data visualization. Thanks. 

[Smita Santram Sontakke]

Hi Shivani,

                  I am looking for how to extract a cross-correlation matrix for an image pair, and it would be really helpful if you could tell us how you have extracted the cross-correlation matrix from PIVlab. 

Thanks,

Smita