[gdal-dev] Extract data from a.dem file

[Carmelo Terrasi]

OK guys, I got it, very helpful!
Thank you so much

2010/9/6 Even Rouault <even.rouault at mines-paris.org>

> Yes , what you see is expected.
>
> The prototype of RasterIO() is :
>
> RasterIO( flag, x, y, width, height, buffer, buffer_width, buffer_height,
> gdal_type, pixel_offset, line_offset)
>
> so that means that you ask the extraction of the window [x, x + with-1] x
> [y,
> y + height -1] to be stored in a buffer_width x buffer_height buffer.
>
> so if you set x to be non-null, you cannot ask for the full XSize to be
> read,
> the maximum value for width is XSize - x.
>
> See
> http://gdal.org/classGDALRasterBand.html#5497e8d29e743ee9177202cb3f61c3c7
> for the full reference.
>
> Le lundi 06 septembre 2010 17:25:31, Carmelo Terrasi a écrit :
> > Hello everybody,
> > I'm trying to figure out how to get elevation from a .dem file.
> >
> > I opened the file:
> > ...
> > pointerToDataSet=(GDALDataset*) GDALOpen("myFile.dem", GA_ReadOnly);
> > ...
> >
> >
> > So I caught a grid as a 371x371 matrix, but I can read only the first
> line,
> > so the first 371 elevations... the error is: *...Access window out of
> range
> > in RasterIO()...*
> >
> > I mean If I put coordinates like (*0*, *somethingelse*) where 0<*
> > somethingelse<*370:
> > ...
> > pointerToBand->RasterIO( GF_Read, 0, *somethingelse*, nXSize, 1,
> elevation,
> > nXSize, 1,  GDT_Float32, 0, 0 );
> > ...
> > that's ok
> >
> >
> >
> > Instead if I put coordinates (*x*, *somethingelse*) where
> > 0<*somethingelse*<370 and
> > 0<*x*:
> > ...
> > pointerToBand->RasterIO( GF_Read, *x*, *somethingelse*
> > , nXSize, 1, elevation, nXSize, 1,  GDT_Float32, 0, 0 );
> > ...
> > that doesn't work :(
> >
> > I opened myFile.dem with a text editor and I've seen the whole matrix as
> a
> > linecode values...
> > There's something I cannot understand obviously, any tips would be really
> > appreciated, thanks in advance,
> > Regards
> > Carmelo
>
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