Valid Detection Probability

[M l]

Hi William,

I am currently doing my Masters on image preprocessing in PIV (a world of which I am completely new to). Love the software and all your videos and papers have made it far easier for a rookie like me to understand so thanks! I'm just wondering how exactly the VDP is calculated for a vector field as I am really struggling to figure out how to quantify errors to compare the effect of my preprocessing so it would be great if I could use VDP as a metric for comparison. As the VDP for each vector is the probability that the highest correlation peak corresponds to the true mean displacement of the particle images/IW, is the VDP for the vector field just the average of the VDP for each vector in the field? Also, I have just updated to version 3.09 and my 'Main tasks quick access' bar is no longer there - is this part of the new update or I suspect it may just be a problem with MacOS. Finally, is there any way to extract the correlation matrix from a single vector. I apologise if these are all silly questions I'm pretty new to this!

Thank you!

[M l]

^Talking about VDP without enabling any of the other validation filters 

[William]

Hi, the vdp definition that I use comes from this book:

https://link.springer.com/book/10.1007/978-3-540-72308-0

It simply is the ratio of valid vectors (as set by the filter thresholds) divided by the total amount of vectors.

The quick access toolbar will be displayed if there is enough space on the screen. I needed some more space for some new elements. 

Yes you can get the correlation matrices for all vectors: Open PIVlab_GUI.m, and in line 80, set do_correlation_matrices to 1. PIVlab should then send the correlation matrices to the matlab workspace after an analysis.

[Joe Farrell]

Hello,

I have modified line 80 of the code, but the correlation matrices variable in my workspace is still a series of empty cells after analysis. Are there any other settings that need to be adjusted?

Thanks!

[William]

Please describe what piv settings you are using.

[Joe Farrell]

I think I have identified the problem. There seems to have been some pathing issue with how I installed PIVlab so that when I use the app to start the program, the program runs from the PIVlab folder in my trash rather than the PIVlab folder in my MATLAB file path. Directly running PIVlab_GUI.m to start the program solved the issue.

Thanks!