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

[Andreas H.]

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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>