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TOA and NDWI

Dear Community,
I want to analyse Sea Ice in Hudson Bay and want to use the NDWI for it. Of course I need to do a TOA Correction first, where the error occurs "The computed reflectance values are outside of the reflected range (0-100). Please review your radiometric calibration and coefficients values and units." What does this mean?
I still get an output, so I tried working on, but whenever I use the Raster Calculator for the statement "(%1-%2)/(%1+%2)" for NDWI, I receive a full black image and the error "bad file in channel assignment". 

What do I have to do to get my results

Bernadette Mederer

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I downloaded Landsat-8 Files from USGS Earth Explorer, which contain Band 1-11 + BQA-TIFF. Then I translated the Bands I need (3,5,6,7; in case I want to do a NDSI) to .pix-Format and merged them. Then I process the TOA and next would have been NDWI.

I noticed my merged Bands do not have metadata. Maybe this is an explaination?
Other than that, I tried to do a TOA manually by calculating gain and offset from the metadata, but this did not work either.

Bernadette Mederer 0 votes
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When using ATCOR it is recommended that you use the mtl file as the input. The Landsat-8 metadata will be read in directly by the ATCOR GUI. The ATCOR tutorial outlines how to correct Landsat-8 imagery - https://support.pcigeomatics.com/hc/en-us/articles/360015824152-ATCOR-Ground-Reflectance-Workflow-Geomatica-2018. 

I would then recommend calculating NDWI using the TOA output image. Once you have completed the processing, you can export a subset of the channels to a new file using Focus > Files > Utility > Translate.

PCI Geomatics 1 vote
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Hello,

I have practically the same problem and I would like to understand, why the error "bad file in channel assignment" occures.

After calculating ATCOR I would like to calculate NDSI, but in Raster Calculater occures this error.

Is something wrong with my file, it's path or format?

 

Bernadett, how did you solve your problem?

Dear PCI Geomatics, the export of channels and creating of a new file did not help me here.

 

Regards, Daria

 

Daria 0 votes
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