Hi, I have a question concerning the export of the chlorophyll a concentration band after using the C2RCC tool.
I am using SNAP 5.0 and Sentinel-2A images. After resampling the image I used the C2RCC tool to process the image. The outcome looks quite accurate with Chlorophyll a concentrations between 0 and 19 mg/m3.
However, when I export the band (as a band subset) as a GEOTiff file and open it in ArcGIS or QGIS, the raster values range between 0 and 2.86 and until now I just could not find out how to export the actual values shown in SNAP.
Any ideas are appreciated!
Thanks!!
SNAP 5.0 is not supported, please upgrade to 6.0 and install all the updates.
Sorry, my mistake, I am using SNAP 6.0 and not 5.0.
Internally in SNAP，the chlorophyll a concentration is automatically transformed with:pow(iop_apig, 1.04) * 21.0 when displayed. When you export it into geotiff or ENVI format, then the original iop_apig (algae pigment) band is exported, so you can apply the equation manually to get Chl-a concentration.
To be more convenient, it is suggested a straightforward conversion in SNAP is more user-friendly.
Hello. I’m new here but I’ve been reading the forum for a long time.
Encountered the same difficulty with values in snap 8.0. Chlorophyll values shown in snap are not the same as when I export to geotiff. Even if I look for conc_chl.img or if I process the mathematical expression with iop_apig they are not the same as in the snap. The result of the iop_apig mathematical expression is equal to the geotiff exported in the conventional way (file-export-geotiff). I didn’t notice any changes.
So I ask: Is there any way to export the chlorophyll concentration band (as geotiff for example) keeping the values without distortion.
Thanks!
Besides that, you better use SNAP 9, please try to convert conc_chl virtual band int a real band before exporting. You can do this by right-click and selecting ‘Convert Band’
Thanks for the feedback 
I had already converted to real band when I got these results. I will update the version and reprocess. If this solves the problem, I’ll let you know here.
Hello!
I redid the processing in the updated version, the results still vary when exported to geotiff. I didn’t mention it but when I do the processing to export I only select the “conc_chl” band. Some warnings about adding flags appear but I refuse and keep only the “conc_chl” band for export. Is there any other band that should be added in the process along with the “conc_chl” to maybe adjust the interval results?
Thanks again for your attention.
In general, you should not ignore the flags. They can have a significant impact on the usability of the data.
But if you don’t need them, the export should be okay as you are doing it.
Can you show the differences by a screenshot. Maybe the difference comes only from the fact that the data is differently displayed by two applications. Have you compared the values?