[gdal-dev] reprojecting coastcolour (/meris) using python via GCPs

[Etienne Tourigny]

On Mon, Feb 17, 2014 at 2:03 PM, Ivan Price <Ivan.Price at noveltis.fr> wrote:

>  Hi Etienne,
>
>
>
> firstly the problem reading the MERIS (actually coastcolour) data was due
> to the fact i was using gdal 1.6, after upgrading to 1.9 i can at least
> list the bands so i guess that 'works'.
>

does it really work or sort of? If not, please file a bug report with an
example data set attached or a link to it.


>
>
> regarding the use of the filesystem, i tried that, however it is slow to
> write out the whole dataset to disk, (i need to treat hundreds of images),
> so i was looking for a way to avoid this.. although it will be my fallback
> option if all else fails..
>

have you tried using a .vrt file?


>
>
> either way i'll reply to the list with what we do in the end
>
>
>
> thanks for your response,
>
>
>
> -i
>
>
>
>
>
>
>
> *De :* Etienne Tourigny [mailto:etourigny.dev at gmail.com]
> *Envoyé :* Monday, 17 February 2014 14:09
> *À :* Ivan Price
> *Cc :* gdal-dev at lists.osgeo.org
>
> *Objet :* Re: [gdal-dev] reprojecting coastcolour (/meris) using python
> via GCPs
>
>
>
> As far as I know, the gdal warp api is not exposed to python.
>
>
>
> I have no idea on reading the MERIS data with the gdal netcdf driver -
> what I the problem?
>
>
>
> But you might be able to use this workaround: instead of creating a source
> dataset using the memory driver, create a file on disk (in gtiff format)
> with GCPS and write data to disk, and then use gdalwarp on that.
>
>
>
> Etienne
>
>
>
> On Mon, Feb 17, 2014 at 6:46 AM, Ivan Price <Ivan.Price at noveltis.fr>
> wrote:
>
>
>
> Hello,
>
>
>
> I am trying to reproject a window inside a coastcolour (=MERIS) image. As
> far as I can see GDAL cannot read the coastcolour data directly, so i am
> reading the coastcolour netcdf in python, building a source dataset using
> the memory driver, adding GCPS (1 for every 10th pixel) and writing the
> data to it, then reprojecting the source dataset to a destination dataset
> which is a spatial subset of the original in wgs84 lat/long.
>
>
>
> This works fine and is relatively fast, but the reprojection is not
> accurate, the results are out by about 6-10 pixels (in various directions).
> On reading the forums it seems if i was using gdalwarp i would be using
> -tps, however the ReprojectImage() function does not seem to offer this
> parameter ? And i don't have the option of using the commandline tool as
> even gdal 1.10 cannot recognise the coastcolour data.
>
>
>
> So i guess i have 2 questions.. has anyone had any success reading
> coastcolour data with the gdal command line tools, and secondly:
>
>
>
> how can i get ReprojectImage() to be more accurate, given i have a GCP for
> every pixel ?
>
>
>
> thanks and regards,
>
>
>
> -ivan
>
>
>
>
>
>
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>
>
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