If, as Victor indicates, BandMathX is not taking no-data values into account, this has to be considered an error, thus my request is not a desirable feature but an error report. Doing 45.5/no-data = 3.4028234663852886e+38 is an error! By now I'm using gdal_edit.py to set 3.4028234663852886e+38 as no-data value after using BandMathX, but this is very inelegant and not really that helpful as OTB applications (such as DimensionalityReduction) do not recognize the no-data (NA) values as such either...
I read the doc on ManageNoData but found 2 problems: 1. As far as I understand, ManageNoData creates only 1 layer (am I wrong?), which implies that the presence of 1 no-data value in 1 single band would mask out the entire pixel. This can make sense in some cases, but certainly not in many others. Consider the case of a time series of NDVI "images": you normally do not want to drop the entire time series just by 1 missing observation represented as NA. In the case of R, the user can set, for a giving operation, na.rm=TRUE or FALSE. i.e., mean(1,2,3,NA, na.rm=TRUE) = mean(1,2,3), while mean(1,2,3,NA, na.rm=FALSE)=NA I think OTB should incorporate this type of no-data management, as there are always no-data values in mages. 2. I do not see how other OTB applications can take the mask generated by ManageNoData, in particular BandMathX itsel or DimensionalityReduction. Agus On Mon, Jan 7, 2019 at 10:15 AM Poughon Victor <[email protected]> wrote: > > Hi Agustin, > > BandMathX does not read no-data metadata and handles no-data value just like > regular values. It would be a nice feature to add to the application. > > In the meantime, you can modify your expression to conditionally ignore those > value but it might be a bit tricky since your nodata value is FLOAT_MAX. Have > a look at the ManageNoData application or even gdal_translate which can help > you with that. > > Best, > > Victor Poughon > > ________________________________________ > De : [email protected] [[email protected]] de la part de > Agustin Lobo [[email protected]] > Envoyé : vendredi 4 janvier 2019 14:48 > À : [email protected] > Objet : [otb-users] No data handling in BandMathX > > Hi! > Having an operation such as im1/im2 > where both im1 and im2 are tif multi-spectral images with 0 set as > no-data value, otbcli_BandMathX complains about > "Generated 0 Underflow(s) And 836 Overflow(s)" > and the resulting tif image does not have the 3.4028234663852886e+38 > value set as no-data (actually, does not have any value set as > no-data...). > Why? > This is inconvenient, is there any way to specify BandMathX to take the > no-data values into account so that any operation with a no-data value > becomes no-data for a given pixel in a given band? > > Agus > > -- > -- > Check the OTB FAQ at > http://www.orfeo-toolbox.org/FAQ.html > > You received this message because you are subscribed to the Google > Groups "otb-users" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/otb-users?hl=en > --- > You received this message because you are subscribed to the Google Groups > "otb-users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > > -- > -- > Check the OTB FAQ at > http://www.orfeo-toolbox.org/FAQ.html > > You received this message because you are subscribed to the Google > Groups "otb-users" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/otb-users?hl=en > --- > You received this message because you are subscribed to the Google Groups > "otb-users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. -- -- Check the OTB FAQ at http://www.orfeo-toolbox.org/FAQ.html You received this message because you are subscribed to the Google Groups "otb-users" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/otb-users?hl=en --- You received this message because you are subscribed to the Google Groups "otb-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
