[GRASS-dev] [GRASS GIS] #3469: i.atcorr: Sentinel-2 support broken on some systems

[GRASS GIS]

#3469: i.atcorr: Sentinel-2 support broken on some systems
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  Reporter:  sbl          |      Owner:  grass-dev@…
      Type:  defect       |     Status:  new
  Priority:  normal       |  Milestone:  7.4.0
 Component:  Packaging    |    Version:  unspecified
Resolution:               |   Keywords:  i.atcorr
       CPU:  Unspecified  |   Platform:  Unspecified
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Comment (by sbl):

 Replying to [comment:8 mmetz]:
 > The symptom can be cured by using double precision floating point
 variables throughout. Currently, i.atcorr uses single precision floating
 point variables. When using double precision floating point variables,
 Debian testing produces reasonable results. However, these results differ
 from Fedora 27, also using double precision floating point variables
 throughout. I would say that both results (Debian testing and Fedora 27)
 are slightly wrong because of the numerical instability of the 6s code in
 combination with the sentinel-2 parameters.

 Would you be able to provide a patch with those changes? I would not mind
 slightly wrong results, just I am able to proceed. I can update the
 computation once this is properly fixed...

 > I suggest to review the parameters for sentinel-2 as used by i.atcorr.
 > I also suggest to review i.atcorr. The code has been translated from
 Fortran to C++ and might need some manual adjustments.

 I will happily test any fixes on various systems!

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Ticket URL: <https://trac.osgeo.org/grass/ticket/3469#comment:9>
GRASS GIS <https://grass.osgeo.org>