[gdal-dev] re-gridding to a coarser grid

[Brian Case]

Andreas

I think thats referring to my suggestion of GMT to do part of the work






On Thu, 2011-12-15 at 14:00 +0100, Andreas H. wrote:
> Joaquim,
> 
> > nearneighbor is not really a good thing to use. Grid it with surface.
> 
> What do you mean by "grid it with surface"? In my GDAL (1.8.1), I only
> have the following choices:
> 
>    Available resampling methods:
>        near (default), bilinear, cubic, cubicspline, lanczos.
> 
> thanks for your insight,
> 
> Andreas.
> 
> >
> > Joaquim
> >
> > Sent from my iPadiola
> >
> > On 14/12/2011, at 18:32, "Andreas H." <lists at hilboll.de> wrote:
> >
> >> Travis,
> >>
> >> yes, thanks, I had already found that in the documentation. I'm just
> >> wondering what e.g. 'bilinear' means when I go from a fine to a coarse
> >> grid? If GDAL works in terms of "nodes", then I would assume 'bilinear'
> >> means interpolation, which in turn would be a very different result from
> >> working in terms of "cells" and then taking e.g. the average of all
> >> "old" cells in the "new" grid.
> >>
> >> I hope you see my problem / question.
> >>
> >> Thanks for you insight,
> >> Andreas.
> >>
> >> Am 14.12.2011 16:35, schrieb Travis Kirstine:
> >>> Andreas,
> >>>
> >>> Yes gdalwarp support various resampling methods
> >>>
> >>> To use different resampling methods use the -r flag followed by the
> >>> method
> >>>
> >>> eg
> >>>
> >>> gdalwarp -r near ..............
> >>> gdalwarp -r bilinear .............
> >>>
> >>> etc...
> >>>
> >>>
> >>>
> >>>
> >>> On 14 December 2011 08:26, Andreas H. <lists at hilboll.de> wrote:
> >>>> Travis,
> >>>>
> >>>> thanks for your answer!
> >>>>
> >>>> Regarding the resampling methods: Do they all just interpolate the
> >>>> data? I
> >>>> mean, when downsampling, usually I would use mean() or something
> >>>> similar
> >>>> to fill the new (coarser) grid cells. Doas gdalwarp actually do this
> >>>> and
> >>>> I'm not able to understand the documentation, or is it different?
> >>>>
> >>>> Thanks again!
> >>>> Andreas.
> >>>>
> >>>>
> >>>>> Andreas,
> >>>>>
> >>>>> gdalwarp can be used to resample images using the -tr flag or -ts
> >>>>> flag.
> >>>>>
> >>>>> For example resample 1m image to 10m using cubic resampling and
> >>>>> "target resolution'
> >>>>>
> >>>>> gdalwarp -r cubic -tr 10 10 input_1m.tif output_10m.tif
> >>>>>
> >>>>> You may have an issue determining the output resolution as I believe
> >>>>> the resolution will be in decimal degrees rather than arc-seconds.
> >>>>>
> >>>>> Regards
> >>>>>
> >>>>> On 13 December 2011 14:52, Andreas H. <lists at hilboll.de> wrote:
> >>>>>> Hi,
> >>>>>>
> >>>>>> let's say I have a GeoTIFF file with a global grid in a 30
> >>>>>> arc-second
> >>>>>> resolution. Which would be the appropriate GDAL command to spatially
> >>>>>> down-sample this file to say 0.125°?
> >>>>>>
> >>>>>> Thanks for your insight,
> >>>>>> Andreas.
> >>>>>> _______________________________________________
> >>>>>> gdal-dev mailing list
> >>>>>> gdal-dev at lists.osgeo.org
> >>>>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
> >>>>>
> >>>>
> >>>>
> >>>> _______________________________________________
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> >>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
> >>
> >> _______________________________________________
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> >>
> >
> 
> 
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