Average NDVI from a polygon | Planet Community

Hello,

I’m getting started accessing the Process API (S2L1C) and I need to get the minimum, maximum and average ndvi from a polygon.

I’ve already getting the TIFF file with the desired colors, but I don’t know where to start to get those values in the response.

I’m using CURL and PHP.

Any help would be appreciated.

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Hi @marcos.fbc,

the easiest way is to use a dedicated API for this - Statiatical API.

The other option is using updateOutputMetadata function of the custom script as demonstrated in Tip 6 in this blog:

Medium – 15 Jun 21

Custom scripts: faster, cheaper, better!

15 tips for better scripts and more responsive requests

Reading time: 7 min read

Thanks for your quick response.

I`ll try both today.

Hi @gmilcinski,

Thanks again for your response.

I’m trying to use Statiacical API, but when I changed the region using GEOMETRY the response was empty.

Actually I needed to add RESX and RESY to my request as well.

http://services.sentinel-hub.com/ogc/fis/4f9e0919-3206-MASKED?LAYER=VEGETATION-INDEX-NDVI&STYLE=INDEX&CRS=EPSG:3857&TIME=2018-11-15%2F2020-05-15&GEOMETRY=POLYGON((-54.08952876561413 -27.98739282040455,-54.08336551369231 -27.98760544600711,-54.08459142114501 -27.98144772947314,-54.08738735387322 -27.97536276995694,-54.08843974280309 -27.97533191400677,-54.08908634398883 -27.97588577227436,-54.09016603092668 -27.97696274098633,-54.09139788028573 -27.97760384874638,-54.08986613010527 -27.98277768003278,-54.08952876561413 -27.98739282040455))&MAXCC=5&RESX=512&RESY=512

Any ideas why is it happening?

There are several problems in your request:

CRS is defined as EPSG:3857, yet your geometry is provided in EPSG:4326

geometry should be provided in latitude/longitude order

RESX and RESY should not appear in Statistical API, used RESOLUTION instead

RESOLUTION should be provided in the same units as the CRS, e.g. in degrees in your case; there is an exception in case of Statistical API, that you can use RESOLUTION=10m if you want us to give a best try to convert these “10 meters into degrees at your latitude”

Applying all of this you get a request, that works:

http://services.sentinel-hub.com/ogc/fis/4f9e0919-3206-4690-MASKED?LAYER=VEGETATION-INDEX-NDVI&STYLE=INDEX&CRS=EPSG:4326&TIME=2018-11-15%2F2020-05-15&GEOMETRY=POLYGON((-27.98739282040455 -54.08952876561413, -27.98760544600711 -54.08336551369231, -27.98144772947314 -54.08459142114501, -27.97536276995694 -54.08738735387322, -27.97533191400677 -54.08843974280309, -27.97588577227436 -54.08908634398883, -27.97696274098633 -54.09016603092668, -27.97760384874638 -54.09139788028573, -27.98277768003278 -54.08986613010527, -27.98739282040455 -54.08952876561413))&MAXCC=5&RESOLUTION=10m

Note that I have masked part of your instance ID to prevent other readers of this forum to abuse it.

@gmilcinski,

I already tested here and it’s working fine.

Thank you for your help

Hi guys

Did you have any examples of the kinds of results were generated here?