Selon Knut-Frode Dagestad <knutfrodesop...@hotmail.com>: > Even, > > Thank you. That clarifies, and motivates use of the MEM format. > I gradually start to understand that GDAL is generally more > file-oriented than memory-oriented. > > Then I have one last question for this thread: > As mentioned in another post, for some formats (e.g. Envisat) both the > image data and GCP's are read by GDAL. > What is then the reason why reprojecting with API or gdalwarp does not > work, and why this (and other) format is classified as "not > georeferenced" in the table of supported raster formats?
Ah, the doc is sometimes incorrect or lags behind the code. If you see inconsistencies, please file a ticket. > > My theory is that this is because polynomial fit between row/col and > lon/lat does not work since there are errors (contradictions) in the > list of GCP's (e.g.: http://trac.osgeo.org/gdal/ticket/3709). > Or is there another explanation? Yes, this is a possibility. If the GCPs are incorrect, the algorithm may not manage to "invert" the transformation. But I would have assumed that this would lead to a more explicit error message than the one you get. Perhaps you can try playing with the -tps or -order option of gdalwarp, but if the GCPs are incorrect, it is a bit useless of course... > > Best regards from Knut-Frode > > > > > On 07.04.2011 13:31, Even Rouault wrote: > > Selon Knut-Frode Dagestad<knutfrodesop...@hotmail.com>: > > > >> Hi Even, > >> > >> On 06.04.2011 20:21, Even Rouault wrote: > >>> You can certainly write a (non-GDAL) reader in Python, but of course, you > >>> won't be able to benefit from the GDAL API with the "dataset" returned by > >> your > >>> reader, or using them in software that use the GDAL API. > >> > >> But if I use the GDAL API to create a GDAL Dataset and then insert a > >> matrix of data (read with non-GDAL code), and further add some > >> georeferencing or tie-points, it seems to me that I then can utilize > >> GDAL API functionality for e.g. reprojecting, subsetting and exporting, > >> just the same way as if it was read with a GDAL-driver? > > > > Ok, I didn't understand well what you meant before. You could for example > create > > a MEM dataset ( http://gdal.org/frmt_mem.html ) and feed it with matrix of > data > > and georeferencing. If your data is too big and cannot fit entirely into > RAM, > > then you'll have to go with a temporary file, such as geotiff. > > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev > _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
