I could not access the band 's pixels

EO Products / Scripts
1

I am needing to apply a kind of “validations” in the request script, I didn’t get anywhere though.

e.g: I need to get the standard deviation of a band using a function and its return should be less than 130, if it’s true, another comparison get done.

The problem is: I couldn’t find any way to access the pixels of the band to calculate the standard deviation, the pixels should be an array.

Someone have any idea how can I get the all pixels to apply my function?

Thank you in advance! :grin:

2

I have a bit of a hard time understanding the challenges you have.
Can you copy-paste here your full script, so that we can try it out, then state, what exactly you would like to add to this script.

4

I could not develop a script yet, I’ll write an script example of my idea:

const standard_deviation = (band) => // here goes the formula using band pixels

if (standard_deviation(B02) < 200) {
    if (standard_deviation(B08) < 100) {
	// ... more validations
    }
}

Is that possible to access band pixels on script request?

5

I am not completely sure I understand exactly what you are trying to achieve, but if you would like to observe distribution of values for some band, there is a service which might suit your needs:

https://www.sentinel-hub.com/develop/documentation/api/fis-request

FIS performs statistical analysis over some area and returns the results. Is this what you are looking for?

6

Another option is to use multi-temporal processing, where you browse through all the values of the pixel and you simply calculate standard deviation.
See an example of a multi-temporal script:

7

Well, I need for statistical analysis, I’ll see that link you sent, I can not say It if It is what I need in my case.

8

I took a look in the example script but I did not find that part of code where calculates the standard deviation could you explain to me please?

9

This part loops through all the values at the specific location (pixel). In the given example a simple “max” is calculated. You can evolve this to create standard deviation

function evaluatePixel(samples) {  
  var max = 0;
  for (var i=0;i<samples.length;i++) {
      var ndvi = calcNDVI(samples[i]);
    max = ndvi > max ? ndvi:max;
  }

Not all JavaScript functions are supported, but perhaps worth to check if the example provided here would work in your case:

If not, I am sure you can find other examples on how to calculate standard deviation from an array or values.

10

Thank you! I’ll try to implement what I need and tell you as soon as possible if I got success :smiley: