Hi guys. Excuse me for a simple question.

In the module “Raster->Export->Extract pixel values”, if I choose the “mean” of the “Pixel value aggregation method”, the “std” term in the export file represents the standard deviation. But how did “std” calculate? Divided by (N - 1) or N?

PS: N is the square of the window size.

Thank you.

That’s from the source code:

```
Math.sqrt(sumSigma / (numGoodPixels - 1))
```

So it is **N-1**.

Thank you very much, Marco!

Hi, Marco. There is an another question. How and where can I study the source code or algorithms of functions or processing principles in SNAP? Thanks.

It is all on GitHub. It is split in multiple repositories: https://github.com/senbox-org

Maybe these wiki page are also of interest for you: https://senbox.atlassian.net/wiki/spaces/SNAP/pages/8847381/Developer+Guide

I do appreciate your help. Thanks, Marco.