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I'm trying to do Dark Object Subtraction (DOS) for a Spot2 and 4. I have calculated the TOA reflectance and now want to get the at surface reflectance. Using QGIS

I would like to know how I can do DOS in QGIS, can I build a model or use an equation to do this. I have tried doing 6S however SPOT2 and SPOT4 HRV1/2 is not listed in the Pre-defined satellite bands.

  • I would like to know how I can do DOS in QGIS, can I build a model or use an equation to do this. I have tried doing 6S however SPOT2 and SPOT4 HRV1/2 is not listed in the Pre-defined satellite bands. – Barry Sep 1 '14 at 10:08
  • Please put the clarifications in the body of the question (just click edit below the question). It is easy for comments to be hidden when there are many. – BradHards Sep 1 '14 at 10:10
  • @Barry, have you tried ENVI for DOS?? There is also a way to manually insert Gain and Bias values for image calibration in ENVI. – Bytekodes Nov 7 '14 at 10:41
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You can use the semi-automatic classification plugin to do DOS in QGIS. It is a realy nice (user-friendly) and powerful tool that was improved very intesively since last year. It contains a pre-processing section where you can convert DN values to TOA reflectances and perform a DOS by the way.

  • I can see this is an option for Landsat imagery however SPOT imagery does not not come with a MTL file like Landsat does. There is a DIM file that contains the values for Gain/Bias. Is there a way of putting in the values manually instead of selecting a file? – Barry Sep 8 '14 at 11:13
  • @Barry As far as I know you cannot put the values manually in. The folder that you enter as an input directory has to contain a textfile (in this case the MTL) with the metadata and the single bands that you want to process. – JakobT Sep 8 '14 at 18:43

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