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

[Ivan Price]

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'.

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..

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<mailto: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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